[-2, 0, 0, 2]
]
思路，两层循环选出两个数字，对剩下的数字跑双指针。
[三数之和](()
class Solution {
public List fourSum(int[] nums,int target) {
List listArr=new ArrayList<>();
int len=nums.length;
int left,right;
Arrays.sort(nums);
for(int i=0;i
if(i>0 && nums[i] == nums[i-1]) continue;
for(int j=i+1;j
if(j>i+1 && nums[j] == nums[j-1]) continue;
left=j+1;
right=len-1;
while(left
int four=nums[left]+nums[right]+nums[i]+nums[j];
if(four>target){
right–;
}else if(four
left++;
}else{
listArr.add(Arrays.asList(nums[i],nums[j],nums[left],nums[right]));
while(left while(left left++;
