题解 | #三数之和#

1. 用双指针的方式，可以减少一次遍历
2. 注意代码中重复值的处理

#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param num int整型一维数组 
# @return int整型二维数组
#
class Solution:
    def threeSum(self , num: List[int]) -> List[List[int]]:
        # write code here
        len_num = len(num)
        res = []
        if len_num < 3:
            return res
        num.sort()
        for i in range(len_num - 2):
            if (i and num[i] == num[i-1]):
                continue
            left = i + 1
            right = len_num - 1
            while left < right:
                if(num[i] + num[left] + num[right]) ==0:
                    res.append([num[i], num[left], num[right]])
                    while(num[left] == num[left + 1] and (left + 1) < right):
                        left += 1
                    while(num[right] == num[right - 1] and (right - 1) > left):
                        right -= 1
                    left += 1
                    right -= 1
                elif(num[i] + num[left] + num[right] > 0):
                    right -= 1
                else:
                    left += 1   
        return res