22.08.18

BAEKJOON/4803_트리.py

@@ -0,0 +1,50 @@
+from collections import deque
+import sys
+def input(): return sys.stdin.readline().strip()
+
+
+test_case = 1
+while True:
+    N, M = map(int, input().split())
+    if N == 0:
+        break
+
+    edges = [[] for _ in range(N + 1)]
+    for _ in range(M):
+        a, b = map(int, input().split())
+        edges[a].append(b)
+        edges[b].append(a)
+
+    answer = 0
+    visited = [False] * (N + 1)
+    for i in range(1, N + 1):
+        if visited[i]:
+            continue
+        visited[i] = True
+
+        is_tree = True
+        queue = deque([(i, 0)])
+        while queue:
+            here, pre = queue.popleft()
+            for there in edges[here]:
+                if there == pre:
+                    continue
+
+                if visited[there]:
+                    is_tree = False
+                    continue
+                visited[there] = True
+
+                queue.append((there, here))
+
+        if is_tree:
+            answer = answer + 1
+
+    print(f"Case {test_case}: ", end='')
+    if answer == 0:
+        print("No trees.")
+    elif answer == 1:
+        print("There is one tree.")
+    else:
+        print(f"A forest of {answer} trees.")
+    test_case = test_case + 1