Update solution/0018.4Sum/Solution.cpp

Author: KongJHong

solution/0018.4Sum/Solution.cpp

@@ -0,0 +1,40 @@
+class Solution {
+public:
+    vector<vector<int>> fourSum(vector<int>& nums, int target) {
+        int len = nums.size();
+        vector<vector<int>> ans;
+        if(len < 4)return ans;
+        sort(nums.begin(),nums.end());
+        
+        int left;
+        int right;
+        int sum;
+        for(int i = 0;i<len;i++){
+            if(i> 0 && nums[i] == nums[i-1])continue;
+            for(int j = i + 1;j<len;j++){
+                if(j > i+1 && nums[j] == nums[j-1])continue;
+                
+                left = j+1;
+                right = len - 1;
+                
+                while(left < right){
+                    
+                    sum = nums[i] + nums[j] + nums[left] + nums[right];
+                    
+                    if(sum == target){
+                        vector<int> tmp{nums[i],nums[j],nums[left],nums[right]};
+                        ans.push_back(tmp);
+                        
+                        while(left < right && nums[left] == nums[left+1])left++;
+                        while(left < right && nums[right] == nums[right-1])right--;
+                        left++;
+                        right--;
+                    }
+                    else if(sum < target)left++;
+                    else if(sum > target)right--;
+                }       
+            }
+        }
+        return ans;
+    }
+};