59. 最接近的三数之和

##三数之和
class Solution:
    """
    @param numbers: Give an array numbers of n integer
    @param target: An integer
    @return: return the sum of the three integers, the sum closest target.
    """
    def threeSumClosest(self, numbers, target):
        # write your code here
        #双指针，先固定一个值，然后循环判断另外两个值,三数之和和target进行比较，如果小于则更新，否则，不更新
        length = len(numbers)
        min_num,res = sys.maxsize, 0 

        numbers = sorted(numbers)

        #先固定一个值
        for i in range(length):
            value = numbers[i]

            #left，right表示另外两个
            left, right = 0, i - 1
            while left < right:
                sum = numbers[left] + numbers[right] + value 
                
                #在这里进行取差值最小的
                if (abs(sum - target) < min_num):
                    res = sum
                    min_num = abs(sum - target)
                
                #移动指针，控制sum的大小，保持sum - target之间的差值最小
                if sum > target:
                    right -= 1
                else:
                    left += 1
        
        return res