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).

这题只需要求最靠近target的值，重复的情况不需要特别处理（处理也可以提速）。思路和3Sum一致。

代码如下：

class Solution(object):
    def threeSumClosest(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: int
        """
        if not nums or len(nums) < 3:
            return 0
        nums.sort()
        val = sys.maxint
        res = 0
        for i in xrange(len(nums)-2):
            l = i+1
            r = len(nums) -1
            while l < r:
                add = nums[i] + nums[l] + nums[r]
                if abs(target - add) < val:
                    val = abs(target - add)
                    res = add
                if add > target:
                    r -= 1
                else:
                    l += 1
        return res