[852]山脉数组的峰顶索引

参考：

https://leetcode-cn.com/problems/peak-index-in-a-mountain-array/solution/shan-mai-shu-zu-de-feng-ding-suo-yin-by-dtqvv/

二分法查找：

class Solution:
    def peakIndexInMountainArray(self, arr: List[int]) -> int:
        left = 0
        right = len(arr) - 1
        while left <= right:
            mid = (left + right) // 2
            if arr[mid] > arr[mid - 1] and arr[mid] > arr[mid + 1]:
                return mid

            if arr[mid] < arr[mid - 1]:
                right = mid

            if arr[mid] < arr[mid + 1]:
                left = mid

        return -1

```
class Solution:
    def peakIndexInMountainArray(self, A) -> int:
        max_num = -1
        max_index = -1
        for i in range(len(A)):
            if A[i]>max_num:
                max_index = i
                max_num = A[i]
            else:
                break
        return max_index

```
package T852山脉数组的峰顶索引;

public class Solution {
    public int peakIndexInMountainArray(int[] A) {
        int max = -1;
        int index = -1;
        for (int i = 0; i < A.length; i++) {
            if (A[i] > max) {
                max = A[i];
                index = i;
            } else {
                return index;
            }
        }
        return 0;
    }
}