Problem Description: You have a graph with N vertices, M edges. You are then given Q queries, each denoted by three indexes of nodes, A, B, and C. For every such query, you need to output whether it is possible to visit node A, B, and C, i…

Round #25 (Div. 2 only)題意： 給一個 01 矩陣 A[ N ][ M ]。你可以選擇一個 0 轉為 1，轉換後，所有不和任意一個邊界的 0 屬於同一個連通塊 ( 上下左右，且兩者皆 0 視為相鄰 ) 的所有 0 都會轉為 1。問最多可以有多少 1。制約： 1 ≤ N, M ≤ 1000解法： 將…

http://codeforces.com/contest/652/problem/E Shrink each bridge BCC to as a single vertex. If a treasure exists in some BCC, that BCC will be sure able to take that treasure. Otherwise a treasure might be on a bridge linking BCCs, and we wi…

題目的圖論模型是要求將儘量少的點標記，使得刪除任意一點後每個聯通分量有至少一個被標記的點。 我們要發現一般來說標記在割點上不會比較好，而且在同一個點雙連通分量上標記兩個以上的點是無意義的。再說如果一個點雙連通分量含兩個以上的割點，我們可以不…

A vertex biconnected component (bcc) can be defined as a connected component (cc) that is still a cc after any vertex is plucked out of the graph, and usually we would think about the bcc as the largest component that satisfies. An edge bc…