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  1. #include<iostream>
  2. #include<algorithm>
  3.  
  4. #define MaxN 100005
  5. std::pair<int, int> seg[MaxN];
  6.  
  7. int main() {
  8.     freopen("ROBOT.INP", "r", stdin);
  9.     freopen("ROBOT.OUT", "w", stdout);
  10.  
  11.     int M, N; std::cin >> M >> N;
  12.     for(int i = 1; i <= N; ++i) {
  13.         std::cin >> seg[i].first >> seg[i].second;
  14.     }
  15.  
  16.     seg[0] = {0, 0}; seg[N + 1] = {M + 1, M + 1};
  17.     std::sort(seg, seg + N + 2);
  18.  
  19.     int res = 0, last = 0;
  20.     for(int i = 0; i <= N + 1; ++i) {
  21.         if(seg[i].first <= last) last = std::max(last, seg[i].second);
  22.         else {
  23.             res += seg[i].first - last - 1;
  24.             last = seg[i].second;
  25.         }
  26.     }
  27.  
  28.     std::cout << res;
  29.  
  30.     return 0;
  31. }
  32.  
Success #stdin #stdout 0.01s 5312KB
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https://ideone.com/tQ4DwT
language:
C++ (gcc 8.3)
created:
3 days ago
visibility:
public

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