### osource's blog

By osource, history, 6 months ago,

Hello everyone!

While solving this problem, I defined my own comparator function for sorting a vector of coordinates (represented as struct). However I got runtime error upon using the comparator function like this —

struct Point
{
int x,y;
};
int main()
{
vector<Point> v;
sort(v.begin(),v.end(), [&](Point &p1, Point &p2){
if(p1.x!=p2.x)
return p1.x<=p2.x;
return p1.y<=p2.y;
});
}


and also like this —

struct Point
{
int x,y;
};
int main()
{
vector<Point> v;
sort(v.begin(),v.end(), [&](Point &p1, Point &p2){
if(p1.x!=p2.x)
return p1.x<p2.x;
return p1.y<=p2.y;
});
}


But I got AC when I used the comparator like this —

struct Point
{
int x,y;
};
int main()
{
vector<Point> v;
sort(v.begin(),v.end(), [&](Point &p1, Point &p2){
if(p1.x!=p2.x)
return p1.x<=p2.x;
return p1.y<p2.y;
});
}


Can anyone explain why the first 2 comparator definitions gave RE but the third one gave AC?

Submission 1 (RE) — Submission 1

Submission 2 (RE) — Submission 2

Submission 3 (AC) — Submission 3

• -9

By osource, history, 10 months ago,

let's say I have 2 numbers x and y. How do I check if x*y results in an overflow in C++?. Both x and y are long long int.

• +1

By osource, history, 11 months ago,

Hello,

I was solving CSES problemset and am stuck in this question — Question My code — Code

I am getting TLE on 4 test cases. I'm not able to figure out why as I have used standard BFS and therefore the time complexity should be O(m*n). Can someone help me in this?

• -17

By osource, history, 12 months ago,

You have 2 arrays A and B each of size n, that contains integers from 1 to n inclusive. In one move, you can swap corresponding elements of two arrays. Determine if it is possible to have such series of operations (possibly zero) that both arrays contain integers from 1 to n exactly once, if possible print the series of operations (ie indices on which you apply the operations) and -1 if not possible.

eg

A = 3 1 2 1 2

B = 5 4 4 5 3

ans = 3 4

explanation :

after operations

A = 3 1 4 5 2

B = 5 4 2 1 3

Can someone tell me the approach/pseudocode for this?