Thuat toan dijkstra

program TT_Dijkstra;

uses crt;

const max=50;

var

n,s,t: integer;

chon:char;

truoc:array[1 max] of byte;

d :array[1 max] of integer;

a :array[1 max,1 max] of integer;

kt :array[1 max] of boolean;

(******************Nhap So Lieu***********************) procedure NhapSoLieu;

Var

f:text;

fname:string;

i,j:integer;

begin

write('nhap ten tep:') ; readln(fname);

assign(f,fname);

reset(f);

readln(f,n);

for i:=1 to n do

for j:=1 to n do read(f,a[i,j]);

close(f);

end;

(******************In So Lieu**************************) procedure Inketqua;

var i,j:integer;

begin

Write('DUONG DI NGAN NHAT TU',s,'DEN',t);

write(t,'<=');

i:=truoc[t];

while i<>s do

begin

write(i,'<=');

i:=truoc[i];

end;

writeln(s);

writeln('Do dai cua duong di la: ',d[t]);

end;

(*******************************************************) procedure Dijkstra;

var v,u,minp:integer;

begin

write('Tinh duong di tu s= ');

readln(s);

write(' den t=');

readln(t);

for v:=1 to n do

begin (*Khoi tao nhan*)

d[v]:=a[s,v];

truoc[v]:=s;

kt[v]:=false;

end;

truoc[s]:=0;

d[s]:=0;

kt[s]:=true;

while not kt[v] do (*Buoc lap*)

begin

{Tim u la dinh co nhan tam thoi nho nhat}

minp:=maxint;

for v:=1 to n do

begin

u:=v;

minp:=d[v];

end;

kt[u]:=true;

if not kt[t] then

for v:=1 to n do

if (not kt[v]) and (d[u]+a[u,v]<d[v]) then begin

d[v]:=d[u]+a[u,v];

truoc[v]:=u;

end;

end;

end;

(********************************************************) BEGIN

clrscr;

Nhapsolieu;

dijkstra;

Inketqua;

readln;

END