From df7bb622451af847c30f68e2827aa347540f44d0 Mon Sep 17 00:00:00 2001
From: sonoasy <61787171+sonoasy@users.noreply.github.com>
Date: Tue, 23 Nov 2021 22:21:14 +0900
Subject: [PATCH] =?UTF-8?q?[=ED=8A=B8=EB=A6=AC]11=EC=9B=9423=EC=9D=BC?=
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---
 .../4803.cpp"                                 | 65 +++++++++++++++++++
 1 file changed, 65 insertions(+)
 create mode 100644 "11\354\233\22416\354\235\274-\355\212\270\353\246\254/4803.cpp"

diff --git "a/11\354\233\22416\354\235\274-\355\212\270\353\246\254/4803.cpp" "b/11\354\233\22416\354\235\274-\355\212\270\353\246\254/4803.cpp"
new file mode 100644
index 0000000..a6b6605
--- /dev/null
+++ "b/11\354\233\22416\354\235\274-\355\212\270\353\246\254/4803.cpp"
@@ -0,0 +1,65 @@
+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+bool is_tree;
+vector<bool> visited;
+vector<vector<int>> graph;
+
+void dfs(int node, int parent) {
+    if (visited[node]) { //이미 방문한 정점이라면 사이클이 발생한 것
+        is_tree = false; //false 
+        return;//종료
+    }
+
+    visited[node] = true; //방문 처리
+    for (int i = 0; i < graph[node].size(); i++) { //그래프 노드 사이즈만큼
+        if (graph[node][i] != parent) //부모 정점이 아니라면
+            dfs(graph[node][i], node);//dfs
+    }
+}
+
+void printResult(int num, int cnt) {
+    cout << "Case " << num; //케이스 넘버
+    if (cnt == 0) //0이면
+        cout << ": No trees.\n"; //출력
+    else if (cnt == 1)//1이면
+        cout << ": There is one tree.\n";//출력
+    else //그 외
+        cout << ": A forest of " << cnt << " trees.\n";//출력
+}
+
+int main() {
+    int n, m, a, b, test_case = 0; //변수 
+
+    while (true) {
+        test_case++;//테스트 케이스 +1
+
+        //입력
+        cin >> n >> m;
+        if ((n == 0) && (m == 0)) //종료 조건
+            break; //종료 
+        visited.assign(n + 1, false);//초기화
+        graph.assign(n + 1, vector<int>(0));//그래프 초기화 
+        while (m--) { //무방향 그래프
+            cin >> a >> b;//a-b
+            graph[a].push_back(b);//a-b
+            graph[b].push_back(a);//b-a
+        }
+
+        //연산
+        int tree_cnt = 0;
+        for (int i = 1; i <= n; i++) {//n개에 대하여
+            if (visited[i]) //이미 방문한 정점
+                continue;//다음 차례로 
+            is_tree = true; //트리인지 확인
+            dfs(i, -1);//dfs
+            if (is_tree) //트리가 맞다면
+                tree_cnt++;//갯수 +1 
+        }
+
+        //출력
+        printResult(test_case, tree_cnt);
+    }
+}