162. Find Peak Element

题目

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] = -∞.

样例

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

解答

我们可以在最前面和最后面添加一个最小值，这样就可以统一处理数组了。

  int findPeakElement(vector<int>& nums) {       if (nums.size() == 1)    return 0;    nums.insert(nums.begin(), INT_MIN);    nums.insert(nums.end(), INT_MIN);    vector<int>::size_type index ;    int res;    for(index = 1; index < nums.size()-1;index++)        if (nums[index] > nums[index - 1] && nums[index] > nums[index + 1]) {        res = index;        break;    }    return res - 1;   }