class Solution {
public:
    int findPeakElement(vector<int>& nums) {
        int len = nums.size(), left = 0, right = len - 1, mid = (left + right) / 2;
        if (len == 1) return 0;
        if (len == 2) {
            if (nums[0] > nums[1]) return 0;
            else return 1;
        }
        while (left < right) {
            if ((mid + 1 >= len || nums[mid] > nums[mid + 1]) && (mid - 1 < 0 || nums[mid] > nums[mid - 1]))
                return mid;
            else if (nums[mid] < nums[mid + 1]) {
                left = mid + 1;
                mid = (left + right) / 2;
            }
            else {
                right = mid - 1;
                mid = (left + right) / 2;
            }
        }
        return left;
    }
};