트리 풀이

Author: saebyeok0306

BAEKJOON/3Gold/트리.py

@@ -0,0 +1,56 @@
+# 자료 구조, 그래프 이론, 그래프 탐색, 트리, 깊이 우선 탐색, 분리 집합
+# https://www.acmicpc.net/problem/4803
+
+import sys
+from collections import deque
+
+input = sys.stdin.readline
+
+def dfs(start, graph, visit):
+    stack = deque([(start)])
+    is_not_cycle = True
+    while stack:
+        node = stack.pop()
+        if visit[node]:
+            is_not_cycle = False
+            continue
+        
+        visit[node] = True
+
+        for nxt in graph[node]:
+            if not visit[nxt]:
+                stack.append((nxt))
+    
+    return is_not_cycle
+
+tc = 0
+tc_answer = []
+while True:
+    N,M = map(int, input().split())
+    if N == M == 0:
+        break
+
+    tc += 1
+    visit = [False]*(N+1)
+    graph = [[] for _ in range(N+1)]
+    for _ in range(M):
+        a,b = map(int, input().split())
+        graph[a].append(b)
+        graph[b].append(a)
+
+    answer = 0
+    for n in range(1, N+1):
+        if not visit[n] and dfs(n, graph, visit):
+            answer += 1
+    
+    print_answer = f"Case {tc}: "
+    if answer == 0:
+        print_answer += "No trees."
+    elif answer == 1:
+        print_answer += "There is one tree."
+    else:
+        print_answer += f"A forest of {answer} trees."
+    
+    tc_answer.append(print_answer)
+
+print("\n".join(tc_answer))