230722

src/graph/BFS/BOJ13549.java

@@ -0,0 +1,70 @@
+package graph.BFS;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.LinkedList;
+import java.util.Queue;
+import java.util.StringTokenizer;
+
+public class BOJ13549 {
+    static int N;
+    static int K;
+    static int[] times = new int[100_001];
+    static int minTime;
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        StringTokenizer st = new StringTokenizer(br.readLine());
+
+        N = Integer.parseInt(st.nextToken());
+        K = Integer.parseInt(st.nextToken());
+
+        if (N >= K) {
+            System.out.println(N-K);
+            return;
+        }
+
+        bfs();
+        System.out.println(minTime-1);
+    }
+
+    static void bfs() {
+        minTime = 0;
+
+        Queue<Integer> que = new LinkedList<>();
+        que.add(N);
+        times[N] = 1;
+
+        while (!que.isEmpty()) {
+            int now = que.poll();
+
+            if (now == K) {
+                minTime = times[now];
+            }
+
+            int next = now*2;  // 순간이동
+            if (next <= 100_000) {
+                if (times[next] == 0 || times[next] > times[now]) {
+                    que.add(next);
+                    times[next] = times[now];
+                }
+            }
+
+            // 앞 혹은 뒤로 한칸 이동
+            for (int i = 0; i < 2; i++) {
+                if (i == 0) next = now-1;
+                else next = now+1;
+
+                if (next < 0 || next > 100_000) continue;
+
+                if (times[next] == 0 || times[next] > times[now] + 1) {
+                    que.add(next);
+                    times[next] = times[now] + 1;
+                }
+            }
+
+        }
+    }
+
+}