0016. 3Sum Closest.md

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.

O(n^2) Two pointer solution

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number}
 */
var threeSumClosest = function(nums, target) {
    nums.sort((a, b) => a - b);
    // res is initialized as -Infinity, so we know there must be a number that is closer.
    let res = -Infinity;
    
    for(let i = 0; i < nums.length; i++) {
        let low = i + 1, high = nums.length - 1;
        while(low < high) {
            let sum = nums[i] + nums[low] + nums[high];
            if(Math.abs(sum - target) < Math.abs(res - target)) {
                res = sum;
            }
            if(sum < target) {
                low++;
            } else {
                high--;
            }
        }
    }
    return res;
};