1117 Eddington Number

 1 #include<iostream>
 2 #include<vector>
 3 #include<algorithm>
 4 using namespace std;
 5 
 6 int main() {
 7     int n;
 8     cin>>n;
 9     vector<int> v(n),ans(n+1);
10     for(int i = 0; i < n; ++i) cin>>v[i];
11     sort(v.begin(),v.end());
12     int j = 0;
13     for(int i = 0; i <= n; ++i) {
14         while(j < n && i >= v[j]) ++j;
15         ans[i] = n-j;
16     }
17     for(int i = n; i >= 0; --i) {
18         if(ans[i] >= i) {
19             printf("%d",i);
20             break;
21         }
22     }
23     return 0;
24 }