We need to initialize a vector with its size before accessing its elements using indexes. Below is a snippet of part of the code mentioned in this tutorial.

vector < pair <int, int> > pairs; // vector of pairs
int a, b; 
for (i = 0; i < n; i++) { 
   cin >> pairs[i].first >> pairs[i].second;
}

This will throw a run time error. We have to initialize the size of the pairs as shown below.

vector < pair <int, int> > pairs(n); // vector of pairs 
int a, b;  
for (i = 0; i < n; i++) {     
   cin >> pairs[i].first >> pairs[i].second; 
}

Please correct it. This is also mentioned in the topcoder tutorial.

Also, if you don't want to define its size during it...

What do you think about this algorithm?

We want to spend the minimum amount of time in appearing for the contests. (Doesn't matter which one !)

• Make reasonable(v<w) pairs (v,w) for v in V and w in W.
• Sort them on the basis of difference (w-v) in ascending order
• Find the first pair in which any of the contest lies.