Given an array of citations (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 hof 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 = [3,0,6,1,5] Output: 3 Explanation:[3,0,6,1,5] means the researcher has5 papers in total and each of them had received3, 0, 6, 1, 5 citations respectively. Since the researcher has3 papers with at least3 citations each and the remaining two with no more than3 citations each, her h-index is3 .
Note: If there are several possible values for h, the maximum one is taken as the h-index.
<Solution>