[JS] Find Peak Element
2022. 8. 5. 14:17
🔒 문제 (LeetCode 162)
A peak element is an element that is strictly greater than its neighbors.
Given a 0-indexed integer array nums, find a peak element, and return its index. If the array contains multiple peaks, return the index to any of the peaks.
You may imagine that nums[-1] = nums[n] = -∞. In other words, an element is always considered to be strictly greater than a neighbor that is outside the array.
You must write an algorithm that runs in O(log n) time.
Constraints:
- 1 <= nums.length <= 1000
- -231 <= nums[i] <= 231 - 1
- nums[i] != nums[i + 1] for all valid i.
🌊 입출력
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: 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.
🔑 해결
🌌 알고리즘 - 이분탐색
/**
* @param {number[]} nums
* @return {number}
*/
var findPeakElement = function(nums) {
let l = 0;
let r = nums.length - 1;
while(l < r) {
let mid = l + r >>> 1;
if(nums[mid] > nums[mid + 1]) {
r = mid;
} else {
l = mid + 1;
}
}
return l;
};
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