704-binary-search

704. Binary Search (Easy) (https://leetcode.com/problems/binary-search/)

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. Constraints: - 1 <= nums.length <= 10^4 - -10^4 < nums[i], target < 10^4 - All the integers in nums are unique.

• nums is sorted in ascending order.

function search(nums: number[], target: number): number {
  let left = 0,
    right = nums.length - 1;
  let middle = Math.floor((left + right) / 2);
 
  while (right >= left) {
    if (target > nums[middle]) {
      left = middle + 1;
    } else if (target < nums[middle]) {
      right = middle - 1;
    } else {
      return middle;
    }
    middle = Math.floor((left + right) / 2);
  }
 
  return -1;
}
 
// Local check:
console.log(search([-1, 0, 3, 5, 9, 12], 9)); // 4
console.log(search([-1, 0, 3, 5, 9, 12], 2)); // -1
console.log(search([-1, 0, 3, 5, 9, 12], 12)); // 5

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

leetcode