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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. #define ll long long 
  4. #define pll pair<ll,ll>
  5. #define F first
  6. #define S second
  7. #define sz(s) (int)s.size()
  8. #define max(p,q)((p)>(q)?(p):(q))
  9. #define fast ios::sync_with_stdio(0), cin.tie(0)
  10. #define N 100010
  11. ll n;
  12. pll a[N];
  13. int main() {
  14.   fast;cout.tie(0);
  15.   cin>>n;
  16.   for(ll i=0;i<n;i++){ 
  17.     cin>>a[i].F>>a[i].S;
  18.     a[i].S=-a[i].S;
  19.   }
  20.   sort(a,a+n);//第一個越來越大，第二個越來越小
  21.   for(ll i=0;i<n;i++)a[i].S=-a[i].S;
  22.   int ans=1,mx=a[0].S,last=a[0].S;
  23.   bool touch=0;
  24.   for(ll i=1;i<n;i++){
  25.     if(a[i].F>mx+1){
  26.       cout<<-1<<endl;
  27.       return 0;
  28.     }
  29.     if(!touch && a[i].S>last){
  30.       touch=1;
  31.       ans++;
  32.     }
  33.   }
  34.   cout<<ans<<endl;
  35.   return 0;
  36. }
Success #stdin #stdout 0.01s 5384KB
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language:
C++ 4.3.2 (gcc-4.3.2)
created:
1 year ago
visibility:
public

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