[level 2] Title: 후보키, Time: 9.33 ms, Memory: 86.8 MB -BaekjoonHub

Author: CheChe903

프로그래머스/2/42890. 후보키/README.md

@@ -4,7 +4,7 @@
 
 ### 성능 요약
 
-메모리: 78.2 MB, 시간: 7.51 ms
+메모리: 86.8 MB, 시간: 9.33 ms
 
 ### 구분
 
@@ -16,7 +16,7 @@
 
 ### 제출 일자
 
-2025년 10월 14일 20:14:19
+2025년 10월 16일 10:37:07
 
 ### 문제 설명
 

프로그래머스/2/42890. 후보키/후보키.java

@@ -1,56 +1,60 @@
 import java.util.*;
-
 class Solution {
-    List<Set<Integer>> candidateKeys = new ArrayList<>();
-
+    List<Set<Integer>> candidate = new ArrayList<>();
     public int solution(String[][] relation) {
-        int colCount = relation[0].length;
-        boolean[] visited = new boolean[colCount];
-
-        for (int r = 1; r <= colCount; r++) { // 조합 크기 1~N
-            backtrack(0, 0, r, relation, visited);
+        
+        for(int i = 1; i <= relation[0].length; i++) {
+            back(i, 0, 0, relation, new boolean[relation[0].length]);
         }
-
-        return candidateKeys.size();
+        return candidate.size();
     }
-
-    public void backtrack(int depth, int start, int target, String[][] relation, boolean[] visited) {
-        if (depth == target) {
+    
+    public void back(int target, int start, int depth, String [][] relation, boolean [] visited) {
+        
+        if(depth == target) {
             List<Integer> cols = new ArrayList<>();
-            for (int i = 0; i < visited.length; i++) {
-                if (visited[i]) cols.add(i);
+            
+            for(int i = 0; i < visited.length; i++) {
+                if(visited[i]) {
+                    cols.add(i);
+                }
             }
-
-            if (isUnique(cols, relation) && isMinimal(cols)) {
-                candidateKeys.add(new HashSet<>(cols));
-            }
-            return;
+            if(isUnique(cols, relation) && isMin(cols)) {
+                candidate.add(new HashSet<>(cols));
+            }            
         }
-
-        for (int i = start; i < relation[0].length; i++) {
-            if (!visited[i]) {
+        
+        
+        for(int i = start; i < relation[0].length; i++) {
+            if(!visited[i]) {
                 visited[i] = true;
-                backtrack(depth + 1, i + 1, target, relation, visited);
+                back(target, i+1, depth+1, relation, visited);
                 visited[i] = false;
             }
         }
     }
-
-    private boolean isUnique(List<Integer> cols, String[][] relation) {
+    
+    public boolean isUnique(List<Integer> cols, String[][] relation) {
         Set<String> tuples = new HashSet<>();
-        for (String[] row : relation) {
+        for(String row[] : relation) {
             StringBuilder sb = new StringBuilder();
-            for (int c : cols) sb.append(row[c]).append("|");
+            for(int nums : cols) {
+                sb.append(row[nums]).append("|");    
+            }            
             tuples.add(sb.toString());
         }
         return tuples.size() == relation.length;
+        
     }
-
-    private boolean isMinimal(List<Integer> cols) {
-        Set<Integer> current = new HashSet<>(cols);
-        for (Set<Integer> key : candidateKeys) {
-            if (current.containsAll(key)) return false;
+    
+    public boolean isMin(List<Integer> cols) {
+        for(Set<Integer> can : candidate) {
+            Set<Integer> colsSet = new HashSet<>(cols);
+            
+            if(colsSet.containsAll(can)) {
+                return false;
+            }
         }
         return true;
     }
-}
+}