LeetCode H-Index

LeetCode H-Index

题目

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.

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

Hint:

An easy approach is to sort the array first. What are the possible
values of h-index? A faster approach is to use extra space.

代码

class Solution {
public:
    int hIndex(vector<int>& citations) {
        int size = citations.size();
        if (size == 0) return 0;
        vector<int> posibleAnswer(size + 1);
        for (int i = 0; i < size; i++) {
            if (citations[i] > size) posibleAnswer[size]++;
            else posibleAnswer[citations[i]]++;
        }
        int counter = 0;
        for (int i = size; i >= 0; i--) {
            counter += posibleAnswer[i];
            if (counter >= i) return i;
        }
        return 0;
    }
};

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