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Program Spfa
Integer Wei(100, 100)
Integer Way(100)
Integer Queue(100)
Logical Visit(100)
Read *, Nvert, Nedge, Mfrom, Mto
Do I = 1, Nedge
Read *, Lposx, Lposy, Lwei
Wei(Lposx, Lposy) = Lwei
Wei(Lposy, Lposx) = Lwei
End Do
Do I = 1, Nedge
Way(I) = Huge(I)
Visit(I) = .False.
End Do
Queue(1) = Mfrom
Visit(Mfrom) = .True.
Way(Mfrom) = 0
Jqh = 1
Jqt = 2
Do
If (Jqh==Jqt) Go To 7
Icurr = Queue(Jqh)
Jqh = Jqh + 1
If (Jqh==101) Jqh = 1
Visit(Icurr) = .False.
Do I = 1, Nvert
If (Wei(Icurr,I)>0 .And. Wei(Icurr,I)+Way(Icurr)<Way(I)) Then
Way(I) = Way(Icurr) + Wei(Icurr, I)
If (.Not. Visit(I)) Then
Visit(I) = .True.
Queue(Jqt) = I
Jqt = Jqt + 1
If (Jqt==101) Jqt = 1
End If
End If
End Do
End Do
7 Print *, Way(Mto)
End