沒什麼好說的。。就是YZOI1171..
Time Limit: 1000MS | Memory Limit: 10000K | |
Total Submissions: 6225 | Accepted: 2863 |
Description
Node 3 is therefore a Single Point of Failure (SPF) for this network. Strictly, an SPF will be defined as any node that, if unavailable, would prevent at least one pair of available nodes from being able to communicate on what was previously a fully connected network. Note that the network on the right has no such node; there is no SPF in the network. At least two machines must fail before there are any pairs of available nodes which cannot communicate.
Input
Output
The first network in the file should be identified as "Network #1", the second as "Network #2", etc. For each SPF node, output a line, formatted as shown in the examples below, that identifies the node and the number of fully connected subnets that remain when that node fails. If the network has no SPF nodes, simply output the text "No SPF nodes" instead of a list of SPF nodes.
Sample Input
1 2 5 4 3 1 3 2 3 4 3 5 0 1 2 2 3 3 4 4 5 5 1 0 1 2 2 3 3 4 4 6 6 3 2 5 5 1 0 0
Sample Output
Network #1 SPF node 3 leaves 2 subnets Network #2 No SPF nodes Network #3 SPF node 2 leaves 2 subnets SPF node 3 leaves 2 subnets
Source
Code:const shuru='test.in';
shuchu='test.out';
maxn=1001;
maxm=500001;
var ans,dfn,low,headlist:array[0..maxn] of longint;
next,t:array[0..maxm] of longint;
vis:array[0..maxn] of boolean;
pp,tot,x,y,i,j,k,n,m,time,num:longint;
sign:boolean;
procedure init;
begin
for i:=1 to 1000 do headlist[i]:=-1;
fillchar(vis,sizeof(vis),false);
fillchar(ans,sizeof(ans),0);
num:=0;
while x<>0 do
begin
readln(y);
inc(num);
next[num]:=headlist[x];
headlist[x]:=num;
t[num]:=y;
inc(num);
next[num]:=headlist[y];
headlist[y]:=num;
t[num]:=x;
read(x);
end;
end;
function min(a,b:longint):longint;
begin
if a<b then exit(a);
exit(b);
end;
procedure dfs(u,fa:longint);
var i:longint;
begin
inc(time); dfn[u]:=time; low[u]:=time;
vis[u]:=true;
i:=headlist[u];
while i<>-1 do
begin
if not(vis[t[i]]) then begin
dfs(t[i],u);
if low[t[i]]>=dfn[u] then inc(ans[u]);
low[u]:=min(low[u],low[t[i]]);
end
else if t[i]<>fa then low[u]:=min(low[u],dfn[t[i]]);
i:=next[i];
end;
end;
procedure main;
begin
inc(pp);
sign:=true;
init;
ans[1]:=-1;
dfs(1,0);
writeln('Network #',pp);
for i:=1 to maxn do if ans[i]>0 then begin
writeln(' SPF node ',i,' leaves ',ans[i]+1,' subnets');
sign:=false;
end;
if sign then writeln(' No SPF nodes');
writeln;
end;
begin
assign(input,shuru);
assign(output,shuchu);
reset(input);
rewrite(output);
read(x);
while x<>0 do
begin
main;
read(x);
end;
end.