[LeetCode] Find Peak Element

Find Peak Element

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.

解题思路：

这道题挺简单的，只要返回其中一个峰值即可。只需最多扫描一次数组。官方说二分法，我认为是一样的效率的，因为这个数组是随机排列的嘛。注意特殊情况的处理。

class Solution {
public:
    int findPeakElement(const vector<int> &num) {
        int len=num.size();
        //处理特殊情况
        if(len==0||len==1){
            return 0;
        }
        if(num[0]>num[1]){
            return 0;
        }
        if(num[len-1]>num[len-2]){
            return len-1;
        }
        for(int i=1; i<len-1; i++){
            if(num[i]>num[i-1]&&num[i]>num[i+1]){
                return i;
            }
        }
        return 0;
    }
};

[LeetCode] Find Peak Element

原文：http://blog.csdn.net/kangrydotnet/article/details/45011503