All you should know about comparators in C++

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In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.
In C++, comparator should return false if its arguments are equal.

Hope you remember it and will never make such a stupid mistake!

Комментарии (29)

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kpw29

5 лет назад, # |

-16

I didn't know about this before xD

What happens if you return true instead? Runtime error always? Probably not.

→ Ответить

rotavirus

5 лет назад, # ^ |

+52

runtime error sometimes

PHOENIX_5

3 года назад, # ^ |

+34

and TLE sometimes

dorijanlendvaj

+19

and MLE sometimes

Not-Afraid

& segmentation fault sometimes

+23

That's just one form of runtime error, which was already mentioned.

Okay sir.

+14

adam_rajsky

lis05

2 года назад, # ^ |

-20

and CE sometimes

AnandOza

What's an example where this leads to MLE?

+10

30440158

That's pretty rare(resubmitting just gave RE on a later test case) but it did happen to me once.

Ausmosian

Learned it the hard way!!

TLE/RE -> atcoder_26299668

AC -> atcoder_26323495

Abito

16 месяцев назад, # ^ |

-18

and compilation error sometimes

dalex

← Rev. 2 →

https://codeforces.com/blog/entry/70358?#comment-548342 by nishant403

ecemekici

I dont know how any of us survived this far without knowing this.

AmineTrabelsi

4 года назад, # |

It's sad that you only see this kind of posts after you get wrong answer.
Why isn't this mentioned in tutorials, the only way to know about this is to read the documentation.(or blogs like this which you can never find without searching for)

4 года назад, # ^ |

+31

You are supposed to read documentation for the function BEFORE using this function

ouuan

← Rev. 4 →

+44

That's not all you should know about it.

In fact, it should be a Strict Weak Ordering.(transitivity and transitivity of equivalence are also needed).

There's a well-known problem which can be solved by Johnson's rule, and a simple greedy solution which sorts the jobs lacks of transitivity of equivalence. The wrong comparator is $$$P(i, j)=\min(a_i,b_j)<\min(a_j,b_i)$$$ , it should be $$$P(i, j)=\begin{cases}a_i< a_j&\min(a_i,b_j)=\min(a_j,b_i)\\min(a_i,b_j)<\min(a_j,b_i)&\text{otherwise}\end{cases}$$$ .

I don't know any English material about this problem except Wikipedia, so here is this problem in Chinese. In this article (also in Chinese) written by me, I discussed about it.

If anyone is interested in it, I can write a blog about it (in English) :)