16.最接近的三数之和

最接近的三数之和

给你一个长度为 n 的整数数组 nums 和 一个目标值 target。请你从 nums 中选出三个整数，使它们的和与 target 最接近。

返回这三个数的和。

假定每组输入只存在恰好一个解。

示例 1：

输入：nums = [-1,2,1,-4], target = 1
输出：2
解释：与 target 最接近的和是 2 (-1 + 2 + 1 = 2) 。

示例 2：

输入：nums = [0,0,0], target = 1
输出：0

提示：

• 3 <= nums.length <= 1000
• -1000 <= nums[i] <= 1000
• $-10^4$ <= target <= $10^4$

解析

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number}
 */
var threeSumClosest = function (nums, target) {
  let diff;
  let result = nums[0] + nums[1] + nums[2];

  nums = nums.sort((i, j) => i - j);
  for (let i = 0; i < nums.length - 2; i++) {
    let start = i + 1;
    let end = nums.length - 1;

    while (start < end) {
      // 优化
      const sum = nums[i] + nums[start] + nums[end];

      if (sum === target) {
        return sum;
      }
      if (sum > target) {
        if (!diff) {
          diff = sum - target;
          result = sum;
        } else {
          const newDiff = sum - target;
          if (newDiff < diff) {
            diff = newDiff;
            result = sum;
          }
        }
        end--;
      } else {
        if (!diff) {
          diff = target - sum;
          result = sum;
        } else {
          const newDiff = target - sum;
          if (newDiff < diff) {
            diff = newDiff;
            result = sum;
          }
        }
        start++;
      }
    }
  }
  return result;
};