# Java solution in O(n) time

• public class Solution {

``````public int hIndex(int[] citations) {
int size = citations.length;
int count[] = new int[size + 1];
for(int i = 0; i < size; i++){
if (citations[i] >= size) {
count[size]++;
}else{
count[citations[i]]++;
}
}

for(int i = size - 1; i > 0; i--){
count[i] += count[i+1];
}

for (int i = size; i > 0; i--) {
if (count[i] >= i) {
return i;
}
}

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....

• yes,you are right. Not all the citations have an answer,but maybe all the tests that leetcode setted have an answer.

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