LeetCode | 852. Peak Index in a Mountain Array

题目：

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.

题意：

找到数组的peak，然后输出它的index。

代码：

class Solution {
public:
    int peakIndexInMountainArray(vector<int>& A) {
        if(A.size() == 1)
            return 0;
        
        int res = A.size() - 1;
        for(int i = 1; i<A.size(); i++)
        {
            if(A[i - 1] > A[i])
            {
                res = i - 1;
                break;
            }
        }
        return res;
    }
};