每日一题：H指数（思维）

H指数：

class Solution {
public:
    int hIndex(vector<int>& f) {
        int n = f.size();
        sort(f.begin(), f.end());
        for (int i = 0; i < n; i ++ )
        {
            if(f[i] >= n - i)
                return n - i;
        }
        return 0;
    }
};

H指数2：

class Solution {
public:
    int hIndex(vector<int>& f) {
        int l = 0, r = f.size() - 1, n = f.size();
        if(f[r] == 0) return 0;
        while (l < r)
        {
            int mid = l + r >> 1;
            if(f[mid] >= n - mid) r = mid;
            else l = mid + 1;
        }
        return n - r;
    }
};