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  1. #include <bits/stdc++.h>
  2.  
  3. using namespace std;
  4.  
  5. int tc;
  6. int const NMAX = 1e5;
  7. int n, m;
  8. bool exists[1 + NMAX];
  9.  
  10. int main() {
  11.     cin >> tc;
  12.     while(tc--) {
  13.         cin >> n >> m;
  14.         for (int i = 1; i <= n-1; i++) {
  15.             exists[i] = false;
  16.         }
  17.         bool valid = true;
  18.         for (int i = 1; i <= m; i++) {
  19.             int a, b;
  20.             cin >> a >> b;
  21.             if (a > b) {
  22.                 valid = false;
  23.             }
  24.             if (b == a+1) {
  25.                 exists[a] = true;
  26.             }
  27.         }
  28.         if (!valid) {
  29.             cout << -1 << "\n";
  30.             continue;
  31.         }
  32.         int counter = n-1;
  33.         for (int i = 1; i <= n-1; i++) {
  34.             if (exists[i]) {
  35.                 counter--;
  36.             }
  37.         }
  38.         cout << counter << "\n";
  39.     }
  40. }
Success #stdin #stdout 0s 5320KB
comments (?)
stdin
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3
4 2
1 2
3 4
4 2
1 3
2 4
3 1
3 1
stdout
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1
3
-1
https://ideone.com/f8rPrX
language:
C++14 (gcc 8.3)
created:
2 days ago
visibility:
public

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