问题描述

A peak element is an element that is greater than its neighbors.

Given an input array nums, where nums[i] ≠ nums[i+1], find a peak element and return its index.

The array may contain multiple peaks, in that case return the index to any one of the peaks is fine.

找到数组中任意一个波峰值，并返回其索引。

举个例子：

解法1

从上图中，你会发现一个性质：

如果nums[i] > nums[i - 1]，那么它的右边肯定存在波峰，或者nums[i]就是波峰。

同理，左峰同理。

来看下实现：

class Solution {
    public int findPeakElement(int[] nums) {

        int n = nums.length;
        int l = 0, r = n - 1;
        while (l < r){
            int mid = l + r + 1 >> 1;
            if (nums[mid] > nums[mid - 1]) l = mid;
            else r = mid - 1;
        }
        return r;
    }
}

Enjoy it !