POJ2394 Checking an Alibi ——最短路——Pku2394

单源最短路的SPFA算法即可。

CODE

Program Alibi;

Const 

	maxn=1000;

Var

	i,j,k,m,n,f,p,c,o,r,d		:Longint;

	pre,other,last,dist,data	:Array[1..maxn*2]of Longint;

	ans,place					:Array[1..maxn]of Longint;

	

Procedure Spfa;

var 

	seq				:Array[1..maxn*10]of Longint;

	h,t				:Longint;

begin

	h:=0;t:=1;seq[1]:=1;

	fillchar(dist,sizeof(dist),127);

	dist[1]:=0;

	while h<t do 

		begin	

			inc(h);

			i:=seq[h];

			j:=last[i];

			while j<>0 do

				begin

					k:=other[j];

					if dist[k]>dist[i]+data[j] then 

						begin	

							inc(t);seq[t]:=k;

							dist[k]:=dist[i]+data[j];

						end;

					j:=pre[j];

				end;

		end;

end;

	

BEGIN

	readln(f,p,c,m);

	for i:=1 to p do 

		begin

			readln(o,r,d);

			inc(k);pre[k]:=last[o];last[o]:=k;other[k]:=r;data[k]:=d;

			inc(k);pre[k]:=last[r];last[r]:=k;other[k]:=o;data[k]:=d;

		end;

	Spfa;

	k:=0;

	for i:=1 to c do 

		readln(place[i]);

	for i:=1 to c do 

		if dist[place[i]]<=m then 

			begin

				inc(k);

				ans[k]:=i;

			end;

	writeln(k);

	for i:=1 to k do writeln(ans[i]);

END.