solve: 코딩테스트 문제 풀이 - 12일차

Author: OhChangEun

2025-08-24/오창은/[solved] 백준_A B.java

@@ -0,0 +1,28 @@
+import java.io.*;
+
+public class Main {
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        String[] parts = br.readLine().split(" ");
+
+        int A = Integer.parseInt(parts[0]);
+        int B = Integer.parseInt(parts[1]);
+
+        int count = 1;
+        while (A < B) {
+            if (B % 10 == 1) {
+                B /= 10;
+            } else if (B % 2 == 0) {
+                B /= 2;
+            } else {
+                break;
+            }
+            count ++;
+
+            //System.out.println(B);
+        }
+
+        int res = (A == B) ? count : -1;
+        System.out.println(res);
+    }
+}

2025-08-24/오창은/[solved] 백준_N과 M (9).java

@@ -0,0 +1,52 @@
+import java.io.*;
+import java.util.*;
+
+public class Main {
+    static int N, M;
+    static int[] inputs;
+    // static Set<int[]> set;
+    static boolean[] visited;
+    static int[] selected;
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+
+        String[] parts = br.readLine().split(" ");
+
+        N = Integer.parseInt(parts[0]);
+        M = Integer.parseInt(parts[1]);
+
+        inputs = new int[N];
+        // set = new HashSet<>();
+        visited = new boolean[N + 1];
+        selected = new int[M];
+        String[] inputParts = br.readLine().split(" ");
+        for (int i=0; i<N; i++) {
+            inputs[i] = Integer.parseInt(inputParts[i]);
+        }
+
+        Arrays.sort(inputs);
+        dfs(0);
+    }
+    public static void dfs(int depth) {
+        if (depth == M) {
+            for (int num: selected) {
+                System.out.print(num +" ");
+            }
+            System.out.println();
+            return;
+        }
+        
+        // 같은 depth 내에서 중복 선택이 되지 않도록
+        int prev = -1;
+        for (int i=0; i<N; i++) {
+            if (!visited[i] && prev != inputs[i]) {
+                visited[i] = true;
+                selected[depth] = inputs[i];
+                prev = inputs[i];
+                dfs(depth + 1);
+                visited[i] = false;
+            }
+        }
+    }
+}

2025-08-24/오창은/[solved] 백준_트리의 부모 찾기.java

@@ -0,0 +1,55 @@
+import java.io.*;
+import java.util.*;
+
+public class Main {
+    static List<List<Integer>> graph;
+    static boolean[] visited;
+    static int[] parent;
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+
+        int N = Integer.parseInt(br.readLine());
+        graph = new ArrayList<>();
+
+        // 1~N
+        for (int i=0; i<=N; i++) {
+            graph.add(new ArrayList<>());
+        }
+
+        for (int i=0; i<N-1; i++) {
+            String[] parts = br.readLine().split(" ");
+            int u = Integer.parseInt(parts[0]);
+            int v = Integer.parseInt(parts[1]);
+
+            graph.get(u).add(v);
+            graph.get(v).add(u);
+        }
+
+        parent = new int[N + 1];
+        visited = new boolean[N + 1];
+        bfs(1);
+
+        for (int i=2; i<=N; i++) {
+            System.out.println(parent[i]);
+        }
+    }
+
+    static public void bfs(int start) {
+        Queue<Integer> queue = new LinkedList<>();
+        queue.offer(start);
+        visited[start] = true;
+
+        while (!queue.isEmpty()) {
+            int parentNode = queue.poll();
+
+            for (int child: graph.get(parentNode)) {
+                if (!visited[child]) {
+                    visited[child] = true;
+                    queue.offer(child);
+                    parent[child] = parentNode;
+                }
+            }
+        }
+    }
+}