题目描述

Follow up for H-Index: What if the citations array is sorted in ascending order? Could you optimize your algorithm?

Hint:

1. Expected runtime complexity is in O(log n) and the input is sorted.

分析

二分查找

代码

    public int hIndex(int[] citations) {

        int n = citations.length;
        int low = 0, high = n - 1;

        while (low <= high) {

            int mid = low + (high - low) / 2;

            if (citations[mid] == n - mid) {
                return n - mid;
            } else if (citations[mid] < n - mid) {
                low = mid + 1;
            } else {
                high = mid - 1;
            }

        }

        return n - low;
    }