Solution.java

/**
 * A peak element is an element that is greater than its neighbors.
 *
 * Given an input array where num[i] ≠ num[i+1], find a peak element and return its index.
 *
 * The array may contain multiple peaks, in that case return the index to any one of the peaks is fine.
 *
 * You may imagine that num[-1] = num[n] = -∞.
 *
 * For example, in array [1, 2, 3, 1], 3 is a peak element and your function should return the index number 2.
 *
 *
 */

public class Solution {
    public int findPeakElement(int[] nums) {
        if (nums.length == 1) {
            return 0;
        }
        if (nums.length == 2) {
            return nums[0] > nums[1] ? 0 : 1;
        }
        if (nums[0] > nums[1]) {
            return 0;
        }
        if (nums[nums.length - 1] > nums[nums.length - 2]) {
            return nums.length - 1;
        }
        for (int i = 1; i < nums.length - 1; i++) {
            if (nums[i] > nums[i - 1] && nums[i] > nums[i + 1]) {
                return i;
            }
        }
        return -1;
    }
}