題目來源

注意點(diǎn)：

1. hash方式的利用
2. 預(yù)先對(duì)數(shù)組進(jìn)行排序
3. 如何對(duì)結(jié)果進(jìn)行去重

源碼如下：

class Solution:
    def threeSum(self, nums: List[int]) -> List[List[int]]:
        nums.sort()
        res = []
        rec_set = set()
        for i in range(len(nums)):
            if i > 0 and nums[i] == nums[i-1]: #去重1
                continue
            cur_sum = 0 - nums[i]
            cur_hash = {}
            for j in range(i+1, len(nums)):
                if nums[j] in cur_hash:
                    if len(res)>0 and nums[j] == res[-1][2] and nums[i]==res[-1][0]: #去重2
                        continue
                    res.append([
                        nums[i], 
                        cur_hash[nums[j]],
                        nums[j]   
                    ])
                else:
                    cur_hash[cur_sum - nums[j]] = nums[j]
        return res