LeetCoed18. Sum of four numbers

Ideas

The same idea as the sum of three , It also uses a double pointer, which is to add an extra layer on the outside for Circulation is enough .

Code

class Solution {
    public List<List<Integer>> fourSum(int[] nums, int target) {
        Arrays.sort(nums);
        int temp = 0;
        int left = 0;
        int j = 0;
        int right = 0;
        List<List<Integer>> res = new ArrayList<>();
        Set<List<Integer>> set = new HashSet<>();
        for(int i =0;i<nums.length-2;i++){
            for(j = i+1;j<nums.length-2;j++){
                left = j+1;
                right = nums.length-1;
                while(right>left){
                    temp = nums[i] + nums[j]+nums[left]+nums[right];
                    if(temp > target){
                        right--;
                    }else if(temp < target){
                        left++;
                    }else{
                        set.add(Arrays.asList(nums[i],nums[j],nums[left],nums[right]));
                        left++;
                        right--;
                    }
                }  
            }
            
        }
        for(List<Integer> a:set){
            res.add(a);
        }
        return res;
    }
}