一天一大 leet(最接近的三数之和)难度:中等 DAY-24

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)

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

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number}
 */
var threeSumClosest = function (nums, target) {
  const len = nums.length
  if (len < 3) {
    return null
  }
  nums.sort((a, b) => a - b)
  let res = target - (nums[0] + nums[1] + nums[2])
  for (let i = 0; i < len - 2; i++) {
    let left = i + 1,
      right = len - 1
    while (left < right) {
      const sum = nums[i] + nums[left] + nums[right]
      if (sum === target) {
        return sum
      } else if (sum < target) {
        // left++  与  while (nums[left] === nums[++left]) 一样
        while (nums[left] === nums[++left]);
      } else {
        // right--  与  while (nums[right] === nums[--right]) 一样
        while (nums[right] === nums[--right]);
      }
      if (Math.abs(sum - target) < Math.abs(res)) {
        res = target - sum
      }
    }
  }
  return target - res
}