1117. Eddington Number(25)-PAT甲级真题

British astronomer Eddington liked to ride a bike. It is said that in order to show off his skill, he has even defined an “Eddington number”, E — that is, the maximum integer E such that it is for E days that one rides more than E miles. Eddington’s own E was 87.

Now given everyday’s distances that one rides for N days, you are supposed to find the corresponding E (<=N).

Input Specification:

Each input file contains one test case. For each case, the first line gives a positive integer N(<=105), the days of continuous riding. Then N non-negative integers are given in the next line, being the riding distances of everyday.

Output Specification:

For each case, print in a line the Eddington number for these N days.

Sample Input:

10
6 7 6 9 3 10 8 2 7 8

Sample Output:

6

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题目解释

E表示有E天骑车超过E公里，求E的最大整数

分析

• 对数组a进行排序，骑车公里数大于等于a[i]的天数有i+1天，超过a[i]-1的天数有i+1天
• 限制条件为a[e]-1>=i+1=>a[e]>i+1

#include 
#include 
#include 

using namespace std;

int main() {
    int num;
    int e = 0;
    cin >> num;
    vector v(num);
    for (int i = 0; i < num; i++) {
        cin >> v[i];
    }
    sort(v.begin(), v.end(), greater());
    while (e < num && v[e] > e + 1)
        e++;
    cout << e << endl;
    return 0;
}```