Problem

There is an integer array which has the following features:

The numbers in adjacent positions are different.
A[0] < A[1] && A[A.length - 2] > A[A.length - 1].
We define a position P is a peek if:

A[P] > A[P-1] && A[P] > A[P+1]
Find a peak element in this array. Return the index of the peak.

 Notice
    The array may contains multiple peeks, find any of them.

Example
Given [1, 2, 1, 3, 4, 5, 7, 6]

Return index 1 (which is number 2) or 6 (which is number 7)

思路

和 Maximum Number in Mountain Sequence一样

    public int findPeak(int[] nums) {
        if (nums == null || nums.length == 0) {
            return 0;
        }

        int start = 0;
        int end = nums.length - 1;

        while (start + 1 < end) {
            int mid = start + (end - start) / 2;
            if (nums[mid - 1] < nums[mid] && nums[mid] > nums[mid + 1]) {
                return mid;
            }
            if (nums[mid - 1] <= nums[mid] && nums[mid] <= nums[mid + 1]) {
                start = mid;
            } else {
                end = mid;
            }
        }

        if (nums[start] > nums[end]) {
            return start;
        }
        return end;
    }