aktuelle Version des Vorlesungsskripts - ZIB

5 Bäume und Wege
THEN w[dope[i]+j] := c
ELSE w[dope[j]+i] := c;
read(inp, i, j, c);
END;
END;
ELSE: {* invalid mode *}
BEGIN
writeln(outp,’Invalid input mode!’);
HALT;
END;
END;{OF CASE}
{====== Initialization ======}
connected := true;
outnodes := n-1;
weight := 0;
FOR i:=1 TO outnodes DO
BEGIN
in_t[i] := 1;
out_t[i] := i+1;
dist[i] := w[i];
END;
{====== Prim’s Algorithm ======}
WHILE (outnodes > 1) AND connected DO
BEGIN
{- determine entering node -}
min := inf;
ind := 0;
FOR i:=1 TO outnodes DO
IF dist[i] < min
THEN BEGIN
min := dist[i];
ind := i;
END;
IF ind = 0
THEN connected := false
ELSE BEGIN
{- augment tree -}
weight := weight + min;
newnode := out_t[ind];
t1 := in_t[ind];
t2 := out_t[ind];
c := dist[ind];
in_t[ind] := in_t[outnodes];
out_t[ind] := out_t[outnodes];
dist[ind] := dist[outnodes];
in_t[outnodes] := t1;
out_t[outnodes] := t2;
dist[outnodes] := c;
outnodes := outnodes - 1;
{- update dist[] and in_t[] -}
FOR i:=1 TO outnodes DO
BEGIN
IF newnode < out_t[i]
THEN c := w[dope[newnode]+out_t[i]]
ELSE c := w[dope[out_t[i]]+newnode];
IF c < dist[i]
THEN BEGIN
in_t[i] := newnode;
dist[i] := c;
END;
END;
END;
END;
{- insert the last edge -}
88