3Sum_Closest.js

// Given an integer array nums of length n and an integer target, find three integers in nums such that the sum is closest to target.

// Return the sum of the three integers.

// You may assume that each input would have exactly one solution.

// Example 1:

// Input: nums = [-1,2,1,-4], target = 1
// Output: 2
// Explanation: The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).

// Example 2:

// Input: nums = [0,0,0], target = 1
// Output: 0
// Explanation: The sum that is closest to the target is 0. (0 + 0 + 0 = 0).

// Constraints:

//     3 <= nums.length <= 500
//     -1000 <= nums[i] <= 1000
//     -104 <= target <= 104

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number}
 */
var threeSumClosest = function (nums, target) {
  nums.sort((a, b) => a - b);
  let closestSum = nums[0] + nums[1] + nums[2];
  for (let i = 0; i < nums.length - 2; i++) {
    let left = i + 1,
      right = nums.length - 1;
    while (left < right) {
      const sum = nums[i] + nums[left] + nums[right];
      if (sum > target) right--;
      else if (sum < target) left++;
      else return target;
      if (Math.abs(closestSum - target) > Math.abs(sum - target)) {
        closestSum = sum;
      }
    }
  }
  return closestSum;
};