[leetcode] 15. 3Sum

 

class Solution(object):
    def threeSum(self, nums):
        """
        :type nums: List[int]
        :rtype: List[List[int]]
        """
        res = []
        for i in range(len(nums)-2):
            for j in range(i+1, len(nums)-1):
                for k in range(j+1, len(nums)):
                    if nums[i] + nums[j] + nums[k] == 0:
                        
                        res.append(sorted([nums[i], nums[j] , nums[k]]))
        
        
        return list(set(map(tuple, res)))

 

=> 브루트포스 방식 : Timeout 

 

class Solution(object):
    def threeSum(self, nums):
        """
        :type nums: List[int]
        :rtype: List[List[int]]
        """
        result = []
        nums.sort()
        
        for i in range(len(nums)-2):
            # 중복 값 건너 뛰기 
            if i > 0 and nums[i] == nums[i-1]: 
                continue 
            
            left, right = i+1 , len(nums) -1 
            
            while left < right: 
            
                sums = nums[i] + nums[left] + nums[right]
                if sums < 0: 
                    left += 1 
                    
                elif sums > 0:
                    right -= 1 
                    
                else: # 정답 # 
                    result.append([nums[i], nums[left], nums[right]])
                    
                    # 중복값 건너 뒤기 
                    while left < right and nums[left] == nums[left+1]:
                        left += 1 
                    
                    while left < right and nums[right] == nums[right-1]:
                        right -=1
                        
                    left += 1
                    right -= 1
                    
        return result

--> Twopoint 방식