'''
Given an array of citations sorted in ascending order (each citation is a non-negative integer) of a researcher, write a function to compute the researcher's h-index.

According to the definition of h-index on Wikipedia: "A scientist has index h if h of his/her N papers have at least h citations each, and the other N − h papers have no more than h citations each."

Example:

Input: citations = [0,1,3,5,6]
Output: 3 
Explanation: [0,1,3,5,6] means the researcher has 5 papers in total and each of them had 
             received 0, 1, 3, 5, 6 citations respectively. 
             Since the researcher has 3 papers with at least 3 citations each and the remaining 
             two with no more than 3 citations each, her h-index is 3.

Note:

If there are several possible values for h, the maximum one is taken as the h-index.

Follow up:

    This is a follow up problem to H-Index, where citations is now guaranteed to be sorted in ascending order.
    Could you solve it in logarithmic time complexity?


'''

class Solution(object):
    def hIndex(self, citations):
        """
        :type citations: List[int]
        :rtype: int
        """
        count = [0 for i in xrange(len(citations) + 1)]
        for c in citations:
            if c >= len(citations):
                count[-1] += 1
            else:
                count[c] += 1
        tmp = 0
        for i in reversed(xrange(len(citations) + 1)):
            tmp += count[i]
            if tmp >= i:
                return i
            
        return 0
        
