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