# LeetCode – H-Index (Java)

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. 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.

Java Solution 1 ```public int hIndex(int[] citations) { Arrays.sort(citations);   int result = 0; for(int i=citations.length-1; i>=0; i--){ int cnt = citations.length-i; if(citations[i]>=cnt){ result = cnt; }else{ break; } }   return result; }```

Java Solution 2

We can also put the citations in a counting sort array, then iterate over the counter array.

```public int hIndex(int[] citations) { int len = citations.length; int[] counter = new int[len+1];   for(int c: citations){ counter[Math.min(len,c)]++; }   int k=len; for(int s=counter[len]; k > s; s += counter[k]){ k--; }   return k; }```
Category >> Algorithms
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• James Alikhani

My solution in Python3:

def get_H_index(citations):
citiations.sort(reverse=True)
n = len(citations)
h_index = 0
for i in range(n):
if citations[i]>i:
h_index += 1
return h_index