BFS 모음 (#80)

* 효빈이의 과외

* 숨바꼭질

* 숨바꼭질

* 케빈 베이컨의 6단계 법칙

Author: asqwklop12

pr/숨바꼭질/Main.java

@@ -0,0 +1,59 @@
+import java.util.*;
+
+public class Main {
+    static int n;
+    static int k;
+    static int[] visited;
+
+    public static void main(String[] args) {
+
+        Scanner sc = new Scanner(System.in);
+        n = sc.nextInt();
+        k = sc.nextInt();
+
+        visited = new int[100001];
+
+        Arrays.fill(visited, -1);
+
+        solve();
+
+    }
+
+    public static void solve() {
+
+        if (n == k) {
+            System.out.println(0);
+            return;
+        }
+
+        Queue<Integer> queue = new LinkedList<>();
+
+        visited[n] = 1;
+        queue.add(n);
+
+        while (!queue.isEmpty()) {
+            int current = queue.poll();
+            int[] m = { current + 1, current - 1, current * 2 };
+            for (int x = 0; x < 3; x++) {
+                int next = m[x];
+                if (next < 0)
+                    continue;
+                if (next > 100000)
+                    continue;
+
+                // 이미 방문했었용
+                if (visited[next] != -1)
+                    continue;
+                if (next == k) {
+                    System.out.println(visited[current]);
+                    return;
+                }
+                visited[next] = visited[current] + 1;
+                queue.add(next);
+
+            }
+        }
+
+    }
+
+}

pr/케빈 베이건의 6단계 법칙/Main.java

@@ -0,0 +1,75 @@
+import java.util.*;
+
+public class Main {
+    static int n;
+    static int m;
+
+    static int[][] friends;
+
+    public static void main(String[] args) {
+
+        Scanner sc = new Scanner(System.in);
+        n = sc.nextInt();
+        m = sc.nextInt();
+
+        friends = new int[n + 1][n + 1];
+
+        for (int i = 0; i < m; i++) {
+            int a = sc.nextInt();
+            int b = sc.nextInt();
+            friends[a][b] = 1;
+            friends[b][a] = 1;
+        }
+
+        solve();
+
+    }
+
+    public static void solve() {
+        int min = Integer.MAX_VALUE;
+        int index = 0;
+
+        for (int i = 1; i <= n; i++) {
+            int length = bfs(i);
+
+            if (length < min) {
+                min = length;
+                index = i;
+            }
+        }
+        System.out.println(index);
+    }
+
+    public static int bfs(int start) {
+        Queue<Integer> q = new LinkedList<>();
+        boolean[] friendShip = new boolean[n + 1];
+        int[] dist = new int[n + 1];
+        Arrays.fill(dist, -1);
+        q.add(start);
+        friendShip[start] = true;
+        dist[start] = 0;
+
+        while (!q.isEmpty()) {
+            int current = q.poll();
+
+            for (int other = 1; other <= n; other++) {
+                if (friendShip[other])
+                    continue;
+                // 친구가 아니라면 넘어갑니다.
+                if (friends[current][other] == 0)
+                    continue;
+
+                friendShip[other] = true;
+                dist[other] = dist[current] + 1;
+                q.add(other);
+            }
+
+        }
+        int ans = 0;
+        for (int i = 1; i <= n; i++) {
+            ans += dist[i];
+        }
+        return ans;
+    }
+
+}

pr/효빈이의 과외/숨바꼭질/Main.java

@@ -0,0 +1,59 @@
+import java.util.*;
+
+public class Main {
+    static int n;
+    static int k;
+    static int[] visited;
+
+    public static void main(String[] args) {
+
+        Scanner sc = new Scanner(System.in);
+        n = sc.nextInt();
+        k = sc.nextInt();
+
+        visited = new int[100001];
+
+        Arrays.fill(visited, -1);
+
+        solve();
+
+    }
+
+    public static void solve() {
+
+        if (n == k) {
+            System.out.println(0);
+            return;
+        }
+
+        Queue<Integer> queue = new LinkedList<>();
+
+        visited[n] = 1;
+        queue.add(n);
+
+        while (!queue.isEmpty()) {
+            int current = queue.poll();
+            int[] m = { current + 1, current - 1, current * 2 };
+            for (int x = 0; x < 3; x++) {
+                int next = m[x];
+                if (next < 0)
+                    continue;
+                if (next > 100000)
+                    continue;
+
+                // 이미 방문했었용
+                if (visited[next] != -1)
+                    continue;
+                if (next == k) {
+                    System.out.println(visited[current]);
+                    return;
+                }
+                visited[next] = visited[current] + 1;
+                queue.add(next);
+
+            }
+        }
+
+    }
+
+}