162.find-peak-element.java

/*
 * @lc app=leetcode id=162 lang=java
 *
 * [162] Find Peak Element
 *
 * https://leetcode.com/problems/find-peak-element/description/
 *
 * algorithms
 * Medium (43.32%)
 * Likes:    1906
 * Dislikes: 2170
 * Total Accepted:    384.9K
 * Total Submissions: 888.5K
 * Testcase Example:  '[1,2,3,1]'
 *
 * A peak element is an element that is greater than its neighbors.
 * 
 * Given an input array nums, where nums[i] ≠ nums[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 nums[-1] = nums[n] = -∞.
 * 
 * Example 1:
 * 
 * 
 * Input: nums = [1,2,3,1]
 * Output: 2
 * Explanation: 3 is a peak element and your function should return the index
 * number 2.
 * 
 * Example 2:
 * 
 * 
 * Input: nums = [1,2,1,3,5,6,4]
 * Output: 1 or 5 
 * Explanation: Your function can return either index number 1 where the peak
 * element is 2, 
 * or index number 5 where the peak element is 6.
 * 
 * 
 * Follow up: Your solution should be in logarithmic complexity.
 * 
 */

// @lc code=start
class Solution {
    public int findPeakElement(int[] nums) {
        int low = 0;
        int high =nums.length-1;
		
		while(low<high){
			int mid = (high+low)/2;

			if(nums[mid]<nums[mid+1]){
				low = mid+1;
			}
			else
			high = mid;
		}

		return low;
	}
}
// @lc code=end