Day12 - 15. 三数之和

题目链接：https://leetcode.cn/problems/3sum/description/

核心方法 ：双指针

#
# @lc app=leetcode.cn id=15 lang=python3
#
# [15] 三数之和
#

# @lc code=start
class Solution:
    def threeSum(self, nums: List[int]) -> List[List[int]]:
        result = []
        nums.sort()
        
        for i in range(len(nums)):
            # 如果第一个元素已经大于0，不需要进一步检查
            if nums[i] > 0:
                return result
            
            # 跳过相同的元素以避免重复
            if i > 0 and nums[i] == nums[i - 1]:
                continue
                
            left = i + 1
            right = len(nums) - 1
            
            while right > left:
                sum_ = nums[i] + nums[left] + nums[right]
                
                if sum_ < 0:
                    left += 1
                elif sum_ > 0:
                    right -= 1
                else:
                    result.append([nums[i], nums[left], nums[right]])
                    
                    # 跳过相同的元素以避免重复
                    while right > left and nums[right] == nums[right - 1]:
                        right -= 1
                    while right > left and nums[left] == nums[left + 1]:
                        left += 1
                        
                    right -= 1
                    left += 1
                    
        return result

# @lc code=end