16. 3Sum Closest

Given an array nums of n integers 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:

Given array nums = [-1, 2, 1, -4], and target = 1.

The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).

Java

public class Solution {
   public int threeSumClosest(int[] nums, int target) {
        int closest = nums[0] + nums[1] + nums[2];
        int diff = Math.abs(closest - target);
        Arrays.sort(nums);
        for (int i = 0; i < nums.length - 2; i++) {
            int start = i + 1;
            int end = nums.length - 1;
            while (start < end) {
                int sum = nums[i] + nums[start] + nums[end];
                int newDiff = Math.abs(sum - target);
                if (newDiff < diff) {
                    diff = newDiff;
                    closest = sum;
                }
                if (sum < target)
                    start++;
                else
                    end--;
            }
        }
        return closest;
    }
}

public class Solution {
   public int threeSumClosest(int[] nums, int target) {
        Arrays.sort(nums);
        int l = 0, m = l + 1, r = nums.length - 1, result = nums[l] + nums[m] + nums[r], diff = Integer.MAX_VALUE;
        while(l < nums.length -2) {
            int sum = nums[l]+nums[m]+nums[r];
            if(Math.abs(sum-target) < diff) {
                result = sum;
               diff=Math.abs(sum-target);
           }
            if(sum == target && m < r) {
                return sum;
            }
            if(sum < target && m < r) {
                m++;
                r = nums.length - 1;
            }
            if(sum > target && m < r) {
                r--;
            }
            if( m == r ) {
                l++;
                m = l + 1;
                r = nums.length - 1;
            }
        }
        return result;
    }
}

class Solution {
    public int threeSumClosest(int[] nums, int target) {
        int result = nums[0] + nums[1] + nums[2];
        int distance = (target - result) & 0x7fffffff; // Math.abs()
        Arrays.sort(nums);
        for (int i = 0; i < nums.length - 2; i++) {
            if (i == 0 || nums[i] != nums[i - 1]) {
                int twoSumTarget = target - nums[i];
                for (int j = i + 1, k = nums.length - 1; j < k;) {
                    int diff = twoSumTarget - nums[j] - nums[k];
                    if (diff == 0) {
                        return target;
                    }
                    else if (diff < 0) {
                        if (-diff < distance) {
                            result = target - diff;
                            distance = -diff;
                        }
                        k--;
                    }
                    else {
                        if (diff < distance) {
                            result = target - diff;
                            distance = diff;
                        }
                        j++;
                    }
                }
            }
        }
        return result;
    }
}