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HELP in implementation of sort STL for vector pair C++
By hell_hacker, history, 7 years ago, In English

I had a vector of pairs. I wanted it sorted in descending according to the first value of the vector. 

sort(a.begin(),a.end(),[](pair<int,int> &left, pair<int,int> &right){
         return left.first >= right.first;
});

This gave me TLE. Sorting it normally 

sort(a.begin(),a.end());

and iterating from the end worked.

Why does the first sorting function give TLE? Do I have to implement it some other way?

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7 years ago, # |
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Auto comment: topic has been updated by hell_hacker (previous revision, new revision, compare).

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7 years ago, # |
  Vote: I like it +1 Vote: I do not like it

sort requires its comparison operator to be strict.

This code should work:

sort(a.begin(),a.end(),[](pair<int,int> &left, pair<int,int> &right){
         return left.first > right.first;
});
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7 years ago, # |
  Vote: I like it +5 Vote: I do not like it

There's no need to write custom comparator inline, because comparators for pair<int,int> are already there. You can simply write sort(a.begin(), a.end(), greater<pair<int,int>>());.

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