LeetCode - 3Sum Closest

Problem description

description

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).

Analysis

This is a simple question similar to 3 Sum, as the output is the closest value, so that we can calculate every triplet and update the value.

Here’s the code:

public class ThreeSumClosest {
  public int threeSumClosest(int[] nums, int target) {
    Arrays.sort(nums);

    int res = nums[0] + nums[1] + nums[2];
    for (int i = 0; i < nums.length; i++) {
      int val = nums[i];

      int left = i + 1, right = nums.length - 1;
      while (left < right) {
        int sum = val + nums[left] + nums[right];
        if (Math.abs(sum - target) < Math.abs(res - target)) {
          res = sum;
        } else if (sum < target) {
          left++;
        } else if (sum > target) {
          right--;
        }
        // miss early return
        else {
          return target;
        }
      }
    }

    return res;
  }
}

What to improve

• be careful about the early return condition.

• should not use previous code and should treat every problem as a brand new problem