Graph Connectivity
Time Limit:8000MS Memory Limit:131072K
Total Submit:1215 Accepted:272
Case Time Limit:3000MS
Description Let us consider an undirected
graph G = < V, E >. At first there is no edge in the graph. You
are to write a program to calculate the connectivity of two different
vertices. Your program should maintain the functions inserting or
deleting an edge.
Input The
first line of the input contains an integer numbers N (2 <= N <=
1000) -- the number of vertices in G. The second line contains the
number of commands Q (1 <= Q <= 20000). Then the following Q
lines describe each command, and there are three kinds of commands:
I u v: Insert an edge (u, v). And we guarantee that there is no edge between nodes u and v, when you face this command.
D u v: Delete an existed edge (u, v). And we guarantee that there is an edge between nodes u and v, when you face this command.
Q u v: A querying command to ask the connectivity between nodes u and v.
You should notice that the nodes are numbered from 1 to N.
Output Output one line for each querying command. Print "Y" if two vertices are connected or print "N" otherwise.
Sample Input
3
7
Q 1 2
I 1 2
I 2 3
Q 1 3
D 1 2
Q 1 3
Q 1 1
Sample Output
N
Y
N
Y
Source POJ Monthly--2006.06.25, Zheng Zhao
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