leetcode hIndexII

视频分析：http://v.youku.com/v_show/id_XMTMzMzI5OTQ1Ng==.html
题干：
Follow up for H-Index: What if the citations array is sorted in ascending order? Could you optimize your algorithm?

Hint:

Expected runtime complexity is in O(log n) and the input is sorted.

代码：

class Solution(object):
    def match(self, citations, index):
        num=len(citations)
        return (True if citations[index]>=num-index else False)
    def findFirstMatch(self, citations, start, end):
        num=len(citations)
        if(start==end):
            if self.match(citations,start):
                return num-start
            else:
                return 0
        if(start+1==end):
            if (not self.match(citations,start) and self.match(citations,end)):
                return num-end
            elif(self.match(citations,start) and self.match(citations,end)):
                return num
            else:
                return 0
        elif(self.match(citations,(start+end)//2)):
            return self.findFirstMatch(citations,start,(start+end)//2)
        else:
            return self.findFirstMatch(citations,(start+end)//2,end)

    def hIndex(self, citations):
        num=len(citations)
        if num<1:
            return 0
        return self.findFirstMatch(citations,0,num-1)