15 三数之和

class Solution:
    def threeSum(self, nums: List[int]) -> List[List[int]]:
        # 暴力解
        n = len(nums)
        res = []
        nums.sort()
        for i in range(n - 2):
            if i > 0 and nums[i] == nums[i - 1]:
                continue
            k = n - 1
            target = -nums[i]
            for j in range(i + 1, n - 1):
                if j > i + 1 and nums[j] == nums[j - 1]:
                    continue
                while j < k and nums[j] + nums[k] > target:
                    k -= 1
                if j == k:
                    break
                if nums[j] + nums[k] == target:
                    res.append([nums[i], nums[j], nums[k]])
        
        return res

class Solution {
    public List<List<Integer>> threeSum(int[] nums) {
        Arrays.sort(nums);
        List<List<Integer>> ans = new ArrayList<>();
        int n = nums.length;
        for(int i = 0; i < n - 2; i++){
            if(i > 0 && nums[i] == nums[i - 1]){
                continue;
            }
            if(nums[i] > 0){
                continue;
            }
            for(int j = i + 1; j < n - 1; j++){
                if(j > i + 1 && nums[j] == nums[j - 1]){
                    continue;
                }
                if(nums[i] + nums[j] > 0){
                    continue;
                }
                for(int k = j + 1; k < n; k++){
                    if(nums[i] + nums[j] + nums[k] == 0){
                        List<Integer> arr = new ArrayList<>();
                        arr.add(nums[i]);
                        arr.add(nums[j]);
                        arr.add(nums[k]);
                        ans.add(arr);
                        break;
                    }
                    else if(nums[i] + nums[j] + nums[k] > 0){
                        break;
                    }
                }
            }
        }
        return ans;
    }
}