5-kokeunho

kokeunho/README.md

@@ -3,5 +3,8 @@
 | 차시 |    날짜    | 문제유형 | 링크 | 풀이 |
 |:----:|:---------:|:----:|:-----:|:----:|
 | 1차시 | 2024.09.28 |  구현  | [킹](https://www.acmicpc.net/problem/1063) | [#1](https://github.com/AlgoLeadMe/AlgoLeadMe-12/pull/1) |
-| 2차시 | 2024.10.01 | 다이나믹 프로그래밍 | [평범한 배낭](https://www.acmicpc.net/problem/12865) | [#5] (https://github.com/AlgoLeadMe/AlgoLeadMe-12/pulls/4) |
+| 2차시 | 2024.10.01 | 다이나믹 프로그래밍 | [평범한 배낭](https://www.acmicpc.net/problem/12865) | [#5](https://github.com/AlgoLeadMe/AlgoLeadMe-12/pull/5) |
+| 3차시 | 2024.10.08 |  구현  | [약수들의 합](https://www.acmicpc.net/problem/9506) | [#14](https://github.com/AlgoLeadMe/AlgoLeadMe-12/pulls/14) |
+| 4차시 | 2024.10.17 |  수학  | [피보나치 수 3](https://www.acmicpc.net/problem/2749) | [#16](https://github.com/AlgoLeadMe/AlgoLeadMe-12/pull/16) |
+| 5차시 | 2024.11.03 |  트리  | [LCA](https://www.acmicpc.net/problem/11437) | [#19](https://github.com/AlgoLeadMe/AlgoLeadMe-12/pull/19) |
 ---

kokeunho/트리/5-kokeunho.py

@@ -0,0 +1,58 @@
+import sys
+input = sys.stdin.readline
+sys.setrecursionlimit(10**5)
+
+n = int(input())
+
+tree = [[] for _ in range(n+1)]
+parent = [[0] * 20 for _ in range(n+1)]
+depth = [0] * (n+1) 
+visited = [False] * (n+1)
+
+for _ in range(n-1):
+    p, c = map(int, input().split())
+    tree[p].append(c)         
+    tree[c].append(p)
+
+def dfs(node, d):
+    visited[node] = True
+    depth[node] = d
+    for i in tree[node]:
+        if not visited[i]:
+            parent[i][0] = node 
+            dfs(i, d + 1)
+
+def sparse_table():
+    for j in range(1, 20):
+        for i in range(1, n+1):
+            if parent[i][j-1] != 0:
+                parent[i][j] = parent[parent[i][j-1]][j-1]
+
+def lca(a, b):
+    if depth[a] < depth[b]:
+        a, b = b, a
+
+    for i in range(19, -1, -1):
+        if depth[a] - depth[b] >= (1 << i):
+            a = parent[a][i]
+
+    if a == b:
+        return a
+
+    for i in range(19, -1, -1):
+        if parent[a][i] != parent[b][i]:
+            a = parent[a][i]
+            b = parent[b][i]
+
+    return parent[a][0] 
+
+dfs(1, 0)
+sparse_table()
+
+m = int(input())
+
+for _ in range(m):
+    a, b = map(int, input().split())
+    print(lca(a, b))
+
+