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 *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.”

For example, given `citations = [3, 0, 6, 1, 5]`

, which means the researcher has `5`

papers in total and each of them had received `3, 0, 6, 1, 5`

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, his h-index is `3`

.

public class Solution { public int hIndex(int[] citations) { int length = citations.length; if (length == 0) return 0; int[] array2 = new int[length+1]; for (int i = 0; i < length; i++) { if (citations[i] > length) { array2[length]++; } else { array2[citations[i]] ++; } } int t = 0; int result = 0; //倒叙开始累加 for (int i = length; i >= 0; i--) { t += array2[i]; if (t >= i) return i; } return 0; } }

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