Leetcode - Array - 162. Find Peak Element（水题）

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本文介绍了一种寻找峰值元素的方法。峰值元素是指比其左右邻居都大的元素。文章详细解释了一个算法，该算法通过在输入数组中查找这样的元素并返回其索引来解决这个问题。

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1. Problem Description

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

Given an input array where num[i] ≠ num[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.

You may imagine that num[-1] = num[n] = -∞.

For example, in array [1, 2, 3, 1], 3 is a peak element and your function should return the index number 2.

输出数组中任意一个大于其左邻右邻的数字的下标。

2. My solution

You may imagine that num[-1] = num[n] = -∞.

利用这句话很容易写出：

int findPeakElement(vector<int>& nums) {
         int len=nums.size();
         const int INF=1<<32-1;
         nums.push_back(-INF);
         int ansidx=0;
         for(int i=1;i<len;i++)
            if(nums[i]>nums[i-1]&&nums[i]>nums[i+1])
               ansidx=i;
         return ansidx;
    }