leetcode 15 3sum & leetcode 18 4sum

3sum:
 1 class Solution {
 public:
     vector<vector<int>> threeSum(vector<int>& nums) {
         vector<vector<int>>result;
          vector<vector<int>>::iterator iter;
          vector<int>Middle;
          int length=nums.size()-;
          sort(nums.begin(),nums.end());
          for(int i=;i<length-;i++) {
              int st=i+,en=length;
              if(i>&&nums[i]==nums[i-])continue;
              while(st<en) {
                  while(st>i+&&nums[st-]==nums[st]) {
                      st++;
                      continue;
                  }
                  while(en<length&&nums[en+]==nums[en]) {
                      en--;
                      continue;
                  }
                  if(st>=en)break;
                  int temp=nums[st]+nums[en];
                  if(temp+nums[i]==) {
                      Middle.push_back(nums[i]);
                      Middle.push_back(nums[st]);
                      Middle.push_back(nums[en]);
                      result.push_back(Middle);
                      Middle.clear();
                      st++;
                  }
                  else
                  if(temp+nums[i]<)
                      st++;
                  else
                  if(temp+nums[i]>)
                      en--;
              }
          }
         return result;
     }
 };

4sum:

 class Solution {
 public:
     vector<vector<int>> fourSum(vector<int>& nums, int target) {
         vector<vector<int>> result;
         vector<int>MiddResult;
         if(nums.size()<)return result;
         sort(nums.begin(),nums.end());
         int length=nums.size();
         for(int i=;i<length-;i++) {
             if(i>&&nums[i]==nums[i-])continue;
         for(int j=i+;j<length-;j++) {
             if(j>i+&&nums[j]==nums[j-])continue;
             int st=j+,en=length-;
             while(st<en) {
                 if(st>j+&&nums[st-]==nums[st]) {
                     st++;
                     continue;
                 }
                 if(en<length-&&nums[en+]==nums[en]) {
                     en--;
                     continue;
                 }
                 int temp=nums[i]+nums[j]+nums[st]+nums[en];
                 if(temp==target) {
                     MiddResult.push_back(nums[i]);
                     MiddResult.push_back(nums[j]);
                     MiddResult.push_back(nums[st]);
                     MiddResult.push_back(nums[en]);
                     result.push_back( MiddResult);
                     st++;
                     MiddResult.clear();
                 }
                 else
                 if(temp<target)
                    st++;
                   else en--;
             }
         }
         }
         return result;
     }
 };