go语言的四数相加等于指定数算法

func foursumcount(A []int, B []int, C []int, D []int) int{
 des :=map[int]int{}
 for _,v:=range A{
  for _,w:=range B{
   des[v+w]++
  }
 }
}

func foursumcount(A []int, B []int, C []int, D []int) int{
 des :=map[int]int{}
 ans:=0
 for _,v:=range C{
  for _,w:=range D{
   ans +=des[-v-w]
  }
 }
}

func fourSumCount(A []int, B []int, C []int, D []int) int {
 des := map[int]int{}
 ans:=0
 for _,v :=range A{//遍历两个数组，将两个数组的和作为一个索引，进行+1操作
  for _,w:=range B{
    des[v+w]++
  }
 }
 for _,v :=range C{//遍历另两个数组，如果这两个数组进行相加的和的相反数在map中不为1,则证明出现过
  for _,w:=range D{
   ans +=des[-v-w]
  }
 }
 return ans//返回总数
}

S = [-1, 0, 1, 2, -1, -4]

[[-1, 0, 1],[-1, -1, 2]]

public class Solution {
    public List<List<Integer>> threeSum(int[] nums) {
        List<List<Integer>> result = new LinkedList<List<Integer>>();
        if(nums.length<3){
            return result;
        }
        Arrays.sort(nums);
        int left=0,right=nums.length-1;
        for(int mid=0;mid< nums.length-2;mid++){
            if(nums[mid]>0) break;
            if(mid == 0 || (mid > 0 && nums[mid] != nums[mid-1])){
                left=mid+1;
                right=nums.length-1;
                while(left<right){
                    if(nums[left]+nums[mid]+nums[right] ==0){
                        result.add(Arrays.asList(nums[mid],nums[left],nums[right]));
                        while (left < right && nums[left] == nums[left+1]) left++;
                        while (left < right && nums[right] == nums[right-1]) right--;
                        left++;
                        right--;
                    }else if(nums[left]+nums[mid]+nums[right]<0){
                        left++;
                    }else if(nums[left]+nums[mid]+nums[right]>0){
                        right--;
                    }
                }
            }
        }
        return result;
    }
}