diff --git "a/2022/Oct/week_1/LeetCode_3Sum_\354\206\220\354\210\230\354\227\260.java" "b/2022/Oct/week_1/LeetCode_3Sum_\354\206\220\354\210\230\354\227\260.java"
new file mode 100644
index 0000000..495df88
--- /dev/null
+++ "b/2022/Oct/week_1/LeetCode_3Sum_\354\206\220\354\210\230\354\227\260.java"
@@ -0,0 +1,30 @@
+package Oct_2022;
+
+import java.util.*;
+
+public class Solution_LeetCode_3Sum {
+	
+	public List<List<Integer>> threeSum(int[] nums) {
+
+	    Set<List<Integer>> set = new HashSet<>();
+	    
+	    if(nums == null || nums.length < 3) return new ArrayList<>(set);
+
+	    Arrays.sort(nums);
+	    
+	    for (int i = 0; i < nums.length-2; i++) {
+	       int j = i + 1;
+	       int k = nums.length - 1;
+	       
+	       while (j < k){
+	           int sum = nums[i] + nums[j] + nums[k];
+	           
+	           if(sum == 0) set.add(Arrays.asList(nums[i], nums[j++], nums[k--]));
+	           else if(sum < 0) j++;
+	           else if(sum > 0) k--;
+	       }
+	    }
+	    
+	    return new ArrayList<>(set);
+	}
+}
\ No newline at end of file
diff --git "a/2022/Oct/week_1/\355\224\204\353\241\234\352\267\270\353\236\230\353\250\270\354\212\244_lv2_\355\233\204\353\263\264\355\202\244_\354\206\220\354\210\230\354\227\260.java" "b/2022/Oct/week_1/\355\224\204\353\241\234\352\267\270\353\236\230\353\250\270\354\212\244_lv2_\355\233\204\353\263\264\355\202\244_\354\206\220\354\210\230\354\227\260.java"
new file mode 100644
index 0000000..5336cf2
--- /dev/null
+++ "b/2022/Oct/week_1/\355\224\204\353\241\234\352\267\270\353\236\230\353\250\270\354\212\244_lv2_\355\233\204\353\263\264\355\202\244_\354\206\220\354\210\230\354\227\260.java"
@@ -0,0 +1,50 @@
+package Oct_2022;
+
+import java.util.*;
+
+public class Solution_Programmers_42890_후보키 {
+	
+	static ArrayList<HashSet<Integer>> candidate;
+	
+    public int solution(String[][] relation){
+        candidate = new ArrayList<HashSet<Integer>>();
+        solve(0, new HashSet<Integer>(), relation);
+
+        return candidate.size();
+    }
+
+    static void solve(int n, HashSet<Integer> hashSet, String[][] relation){
+        if(n == relation[0].length) {
+            for(int i =0; i < candidate.size(); i++)
+                if(hashSet.containsAll(candidate.get(i))) return;
+            
+            HashSet<String> set = new HashSet<>();
+            
+            for(int r = 0; r < relation.length; r++){
+                String temp = "";
+                
+                for(int c : hashSet) temp += relation[r][c] + ",";
+                
+                if(set.contains(temp)) return;
+                
+                set.add(temp);
+            }
+            
+            candidate.add(hashSet);
+            
+            return;
+        }
+        
+        HashSet<Integer> set1 = new HashSet<>();
+        HashSet<Integer> set2 = new HashSet<>();
+        
+        for(Integer value : hashSet){
+            set1.add(value);
+            set2.add(value);
+        }
+
+        solve(n+1, set2, relation);
+        set1.add(n);
+        solve(n+1, set1, relation);
+    }
+}