**Leetcode 275. H-Index II

https://leetcode.com/problems/h-index-ii/description/

这题理解起来比较诡异。。。

二分答案

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