h-index-ii.py

# -*- coding:utf-8 -*-


# 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
        """
        n = len(citations)
        l, r = 0, n-1
        
        while l <= r:
            mid = (l+r)/2
            if citations[mid] >= n-mid:
                r = mid - 1
            else:
                l = mid + 1
        return n-l