An unordered_map issue

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Автор KP56, история, 2 года назад, По-английски

I don't have a lot of experience with c++, but decided to give it a try since I heard it's very good for competitions. My code when used with an older compiler gives a wrong answer and with the new one the solution is correct, but it fails due to a runtime error in test 2. I couldn't find any issue in my code. Am I missing something?

https://codeforces.com/submissions/KP56

KP56
2 года назад
13

Комментарии (9)

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balalaika

2 года назад, # |

You missing link to any code to watch at:)

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why_I

2 года назад, # ^ |

← Rev. 2 →

I have a question.

whenever i write recursive lambda function. it does not work for long long. Like what if i need to return long long type in a dp problem.

for example:-

example code

...

Your code here...

function<ll(int, int)> sldp = [&](int l, int r)
        {
            if(l>r)return 0;
            if(l==r)return a[l];
            ll &res = dp[l][r];
            if(res!=-1)return res;
            else res = max(a[l]-sldp(l+1, r), a[r]-sldp(l, r-1));
            cout << l << " " << r << " " << res << endl;
            return res;
        };

I don't want to write a blog for it that's why i asked here. Is there anyone who can tell the reason.

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jainmilind

2 года назад, # ^ |

← Rev. 2 →

instead of if(l>r)return 0;

try to do if(l>r)return 0LL;

also all the return should have same return type so make sure they are all long long

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Penguin07

2 года назад, # ^ |

You can also use the following

Example

auto fun = [&](int l, int r) -> long long {
    // both return 0
    //        and
    //      return 0LL would be fine
};

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why_I

2 года назад, # ^ |

← Rev. 2 →

I was submitting my code for two sets(II) on cses. and it's giving runtime error. Can you tell me the reason. code

Edit:- maybe i am getting error because of something else.

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Penguin07

2 года назад, # ^ |

The first dimension of your dp has size of $$$505$$$,

const int N = 505;
int dp[N][252500];

but you used it out of bound

if(i==n+1)
{
    return (tot/2==sum);
}else if(dp[i][sum] != -1)return dp[i][sum];

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ldyllic

2 года назад, # |

← Rev. 2 →

Check out a famous blog https://codeforces.com/blog/entry/62393.

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KP56

2 года назад, # ^ |

Thank you very much for this link. I've actually always thought when coding in java (my primary language) that HashMaps (or unordered_maps in this case) operations are always O(1).

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