Leetcode 16 3Sum Closest

Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have exactly one solution.

    For example, given array S = {-1 2 1 -4}, and target = 1.



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

同 Leetcode 15 3Sum ，增加一个target维护最靠近的值。

def three_sum_closest(nums, target)

    ans = nums[0] + nums[1] + nums[2]

    a = nums.sort

    a.length.times do |i|

        j, k = i+1, a.length - 1

        while j < k

            sum = a[i] + a[j] + a[k]

            return sum if sum == target

            ans = sum if (target-sum).abs < (target-ans).abs

            if sum < target

                j += 1

            elsif sum > target

                k -= 1

            end

        end

    end

    ans

end