2024-08-23

tgyuuAn/DFS/등산 마니아.py

@@ -0,0 +1,31 @@
+import sys
+sys.setrecursionlimit(10 ** 6)
+
+def input(): return sys.stdin.readline().rstrip()
+
+N = int(input())
+# N = 30 만 -> O(N*log(N))
+
+tree = [[] for _ in range(N+1)]
+for _ in range(N-1):
+    node1, node2 = map(int, input().split())
+    tree[node1].append(node2)
+    tree[node2].append(node1)
+
+answer = 0
+def dfs(now_idx, visited, tree):
+    global answer
+
+    temp_cnt = 1
+    for next_node in tree[now_idx]:
+        if next_node in visited: continue
+        visited.add(next_node)
+        temp = dfs(next_node, visited, tree)
+        answer += temp * (temp-1) // 2
+        answer += temp * (N-temp)
+        temp_cnt += temp
+
+    return temp_cnt
+
+dfs(1,{1,}, tree)
+print(answer)    

tgyuuAn/README.md

@@ -77,4 +77,5 @@
 | 68차시 | 2024.08.06 |  그리디  | <a href="https://www.acmicpc.net/problem/24337">가희와 탑</a> | https://github.com/AlgoLeadMe/AlgoLeadMe-1/pull/226
 | 69차시 | 2024.08.10 |  누적합, 수학  | <a href="https://www.acmicpc.net/problem/9527">1의 개수 세기</a> | https://github.com/AlgoLeadMe/AlgoLeadMe-1/pull/228
 | 70차시 | 2024.08.16 |  스택  | <a href="https://www.acmicpc.net/problem/22866">탑 보기</a> | https://github.com/AlgoLeadMe/AlgoLeadMe-1/pull/232
+| 72차시 | 2024.08.23 |  DFS + 트리  | <a href="https://www.acmicpc.net/problem/20188">등산 마니아</a> | https://github.com/AlgoLeadMe/AlgoLeadMe-1/pull/238
 ---