# CFR 781 C. Underground Lab ( Ad hoc, Time Stamp, DFS )

Problem - C - Codeforces題意： 給一個圖，要求放 K 個機器人並給出每個機器人的路徑，路徑長至多為 ceil( 2 * N / K )，使得所有節點都被至少一個機器人拜訪過。資料規模： N, M ≤ 2e5解法： 首先把圖轉換成任意一個生成樹。接著進行類似時間戳記的 DFS，…

# IOICJ 108 Where is He! ( Tree, Timestamp )

Problem Description: You are given a tree with N nodes. There are Q queries, with u, v, w, where you want to know the node x such that x is a node in the simple path between u and v, where it is also the nearest to w.Constraints: 1≤T≤50 2≤…

# IOICJ 92 Double path tree ( Ad hoc, Timestamp )

Problem Description: Given a tree, you want to do the least amount of operations to assert that for any two distinct nodes, there are at least two distinct simple paths that connect them.Constraints: 1≤T≤300 3≤n≤1e5 1≤xi,yi≤n A valid tree …

# CFR Educational 2 E. Lomsat gelral ( Smaller to Larger or Time stamp + Mo's Algorithm )

Problem - E - Codeforces The official solution is to simply merge subtrees from the leaves to the root. Using the smaller to larger strategy, where we always merge the smaller subtree towards the larger, the overall time complexity is O( (…