Reversals

#include <bits/stdc++.h>
using namespace std;
int main() {

  int n, m;
  cin >> n;
  cin >> m;
  string s;
  cin >> s;

  for(int i = 0; i < m; i++) {
    int a, b;
    cin >> a >> b;
		a--;
		b--;
    string sub = s.substr(a, b-a+1);
    reverse(sub.begin(), sub.end());
    s = s.substr(0, a) + sub + s.substr(b+1, n); 
  }
  cout << s << endl;
  return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: TIME LIMIT EXCEEDED