1117.md

1117

• 1117 Eddington Number (25 point(s))

#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

int main() {
	int N;
	cin >> N;
	vector<int> v(N);
	for (int n = 0; n < N; n++) {
		cin >> v[n];
	}
	sort(v.begin(), v.end(), [](int a, int b) -> bool { return a > b; });
	int ans = 0;
	while (ans < N && v[ans] > ans + 1) {
		ans++;
	}
	cout << ans << endl;
}

/*
Sample Input:
10
6 7 6 9 3 10 8 2 7 8
Sample Output:
6
*/

下面的代码时错误的

#include <iostream>
#include <algorithm>
#include <map>
#include <vector>
using namespace std;

int main() {
	int N;
	cin >> N;
	vector<int> v(N);
	for (int n = 0; n < N; n++) {
		cin >> v[n];
	}
	sort(v.begin(), v.end());
	map<int, int> mp;
	for (int i = 0; i < v.size(); i++) {
		N--;
		mp[v[i]] = N;
	}
	int ans = 0;
	for (auto it : mp) {
		// cout << it.first << " " << it.second << endl;
		if (it.second >= it.first) {
			ans = it.first;
		}
	}
	cout << ans << endl;
}

/*
Sample Input:
10
6 7 6 9 3 10 8 2 7 8
Sample Output:
6
*/

当输入 5 个 5 时，该程序中 mp[5] = 0，因此会输出 0，实际应该输出 4。（感谢 CC 的测试用例❤）

References

• 1117 Eddington Number (25 point(s))