H-Index II

Desicription

Given an array of citations sorted in ascending order (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.”

Example:

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Input: citations = [0,1,3,5,6]
Output: 3
Explanation: [0,1,3,5,6] means the researcher has 5 papers in total and each of them had
received 0, 1, 3, 5, 6 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, her h-index is 3.

Note:

If there are several possible values for h, the maximum one is taken as the h-index.

Follow up:

  • This is a follow up problem to H-Index, where citations is now guaranteed to be sorted in ascending order.
  • Could you solve it in logarithmic time complexity?

Solution

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class Solution {
public:
int hIndex(vector<int>& citations) {
int left = 0;
int right = citations.size() - 1;
int res = 0;
while(left <= right) {
int mid = (left + right) >> 1;
if(citations[mid] >= citations.size() - mid) {
res = citations.size() - mid;
right = mid - 1;
} else {
left = mid + 1;
}
}
return res;
}
};