852. Peak Index in a Mountain Array

题目描述：

Let's call an array A a mountain if the following properties hold:

• A.length >= 3
• There exists some 0 < i < A.length - 1 such that A[0] < A[1] < ... A[i-1] < A[i] > A[i+1] > ... > A[A.length - 1]

Given an array that is definitely a mountain, return any i such that A[0] < A[1] < ... A[i-1] < A[i] > A[i+1] > ... > A[A.length - 1].

Example 1:

Input: [0,1,0]
Output: 1

Example 2:

Input: [0,2,1,0]
Output: 1

Note:

1. 3 <= A.length <= 10000
2. 0 <= A[i] <= 10^6
3. A is a mountain, as defined above.

解题思路：

题目简单，相当于找到vector中的最大值。

代码：

class Solution {
public:
    int peakIndexInMountainArray(vector<int>& A) {
        for (int i = 1; i < A.size(); ++i) {
            if (A[i] < A[i-1])
                return i-1;
        }
        return A.size()-1;
    }
};