18 4 sum

https://leetcode.com/problems/4sum/submissions/

class Solution {
    public List<List<Integer>> fourSum(int[] nums, int target) {
        Arrays.sort(nums);
        int n = nums.length;
        List<List<Integer>> ans = new ArrayList<>();
        for (int i = 0; i < n - 3; i++) {
            if (i > 0 && nums[i] == nums[i - 1]) {
                continue;
            }
            for (int j = i + 1; j < n - 2; j++) {
                if (j > i + 1 && nums[j] == nums[j - 1]) {
                    continue;
                }
                long sum = (long)target - nums[i] - nums[j];
                int lo = j + 1;
                int hi = n - 1;
                while (lo < hi) {
                    if (lo > j + 1 && nums[lo] == nums[lo - 1]) {
                        lo++;
                        continue;
                    }
                    if (hi < n - 1 && nums[hi] == nums[hi + 1]) {
                        hi--;
                        continue;
                    }
                    
                    int s = nums[lo] + nums[hi];
                    if (s == sum) {
                        ans.add(Arrays.asList(nums[i], nums[j], nums[lo], nums[hi]));
                        lo++;
                        hi--;
                    } else if (s < sum) {
                        lo++;
                    } else {
                        hi--;
                    }
                }
            }
        }
        return ans;
    }
}

会溢出就尼玛离谱