leetcode_162. Find Peak Element

題目：

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.

簡單 不多贅述。注意一個稍特殊的情況是 只有一個元素的話。那麼返回的一定是0.

直接貼代碼：

class Solution {
public:
    int findPeakElement(vector<int>& nums) {
        int pre = nums[0];
        if(nums.size() == 1){return 0;}
        if(nums[0] > nums[1]){
            return 0;
        }
        for(int i = 1; i < nums.size()-1; ++i){
            if(nums[i] > pre && nums[i] > nums[i+1]){
                return i;
            }
            pre = nums[i];
        }
        if(nums[nums.size()-1] > nums[nums.size()-2]){
            return nums.size()-1;
        }
    } 
};