704. Binary Search

Problem

Given an array of integers nums which is sorted in ascending order, and an integer target, write a function to search target in nums. If target exists, then return its index. Otherwise, return -1.

You must write an algorithm with O(log n) runtime complexity.

  Example 1:

Input: nums = [-1,0,3,5,9,12], target = 9
Output: 4
Explanation: 9 exists in nums and its index is 4

Example 2:

Input: nums = [-1,0,3,5,9,12], target = 2
Output: -1
Explanation: 2 does not exist in nums so return -1

  Constraints:

• 1 <= nums.length <= 104

• -104 < nums[i], target < 104

• All the integers in nums are unique.

• nums is sorted in ascending order.

Solution

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number}
 */
var search = function(nums, target) {
    var left = 0;
    var right = nums.length - 1;
    while (left <= right) {
        var mid = left + Math.floor((right - left) / 2);
        if (nums[mid] === target) {
            return mid;
        } else if (nums[mid] > target) {
            right = mid - 1;
        } else {
            left = mid + 1;
        }
    }
    return -1;
};

Explain:

nope.

Complexity:

• Time complexity : O(log(n)).
• Space complexity : O(1).