# Java O(n) solution.

• ``````public class Solution {
public int hIndex(int[] citations) {
int n = citations.length;
int[] indexs = new int[n+1];
for(int i = 0; i < n; i++) {
if(citations[i]>=n) indexs[n]++;
else indexs[citations[i]]++;
}
for(int j = n; j >= 0; j--) {
if(indexs[j] >= j) return j;
if(j!=0) indexs[j-1] += indexs[j];
}
return 0;
}
}``````

• Hi,

I came across a situation: given citations = [3, 1, 7, 8, 9]. What will be the answer be?

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."

When h=3, the definition will be "A scientist has index 3 if 3 of his/her 5 papers have at least 3 citations each, and the other 2 papers have no more than 3 citations each." Obviously wrong....

When h=4, the definition will be "A scientist has index 4 if 4 of his/her 5 papers have at least 4 citations each, and the other 1 papers have no more than 4 citations each." Obviously wrong....

When h=2, the definition will be "A scientist has index 2 if 2 of his/her 5 papers have at least 2 citations each, and the other 3 papers have no more than 3 citations each." Obviously wrong....

• Hi shuyi@cvs, in reality, "A scientist has index h if h of his/her N papers have at least h citations each", this is just the case. The following definition "the other N − h papers have no more than h citations each." just makes it unclear.

• My previous understand(>= and <) is not correct, and the correct should be >= or <=

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