贴 SPFA 代码 -- Fortran 实现

      PROGRAMSPFA
      INTEGERWEI(100,100)
      INTEGERWAY(100)
      INTEGERQUEUE(100)
      LOGICALVISIT(100)
      READ*,NVERT,NEDGE,MFROM,MTO
      DOI=1,NEDGE
        READ*,LPOSX,LPOSY,LWEI
        WEI(LPOSX,LPOSY)=LWEI
        WEI(LPOSY,LPOSX)=LWEI
      ENDDO
      DOI=1,NEDGE
        WAY(I)=HUGE(I)
        VISIT(I)=.FALSE.
      ENDDO
      QUEUE(1)=MFROM
      VISIT(MFROM)=.TRUE.
      WAY(MFROM)=0
      JQH=1
      JQT=2
      DO
        IF(JQH.EQ.JQT)GOTO7
        ICURR=QUEUE(JQH)
        JQH=JQH+1
        IF(JQH.EQ.101)JQH=1
        VISIT(ICURR)=.FALSE.
        DOI=1,NVERT
          IF(WEI(ICURR,I).GT.0.AND.
     $    WEI(ICURR,I)+WAY(ICURR).LT.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.EQ.101)JQT=1
            ENDIF
          ENDIF
        ENDDO
      ENDDO
 7    PRINT*,WAY(MTO)
      END