[POJ1751 Highways]

【题目】:Highways

【来源】:PKU 1751

【关键字】:图论 最小生成树

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【分析】:先把已有边权改为零，再裸prim。

【小结】:prim把kurscal鄙视了.......

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【代码】:

View Code

 1 program project1;
 2 type
 3   rec = record
 4     x, y: longint;
 5   end;
 6 var
 7   n, m, p, tot: longint;
 8   b: array[0..1000] of boolean;
 9   dis: array[0..1000,0..1000] of real;
10   pre: array[0..1000] of longint;
11   v: array[0..1000] of real;
12   a, ans: array[0..1000] of rec;
13 function d(x, y: longint):real;
14 begin
15   d := sqrt(sqr(a[x].x-a[y].x)+sqr(a[x].y-a[y].y));
16 end;
17 procedure init;
18 var
19   i, j, x, y: longint;
20 begin
21   readln(n);
22   for i := 1 to n do readln(a[i].x,a[i].y);
23   for i := 1 to n do
24     for j := 1 to n do
25       dis[i,j] := d(i,j);
26   readln(m);
27   for i := 1 to m do
28     begin
29       readln(x,y);
30       dis[x,y] := 0;
31       dis[y,x] := 0;
32     end;
33 end;
34 procedure prim;
35 var
36    i, j, t: longint;
37    min, temp: real;
38 begin
39   fillchar(b,sizeof(b),false);
40   fillchar(v,sizeof(v),100);
41   v[1] := 0;
42   for i := 1 to n do
43     begin
44       min := maxlongint;
45       for j := 1 to n do
46         if (not b[j]) and (v[j] < min) then
47           begin
48             min := v[j];
49             t := j;
50           end;
51        b[t] := true;
52        inc(tot);
53        ans[tot].x := pre[t];
54        ans[tot].y := t;
55        for j := 1 to n do
56          if not b[j] then
57            begin
58              temp := dis[t,j];
59              if v[j] > temp then begin v[j] := temp; pre[j] := t; end;
60            end;
61     end;
62 end;
63 procedure print;
64 var
65   i: longint;
66 begin
67   //for i := 1 to n do writeln(pre[i],'##');
68   for i := 1 to tot do
69     if dis[ans[i].x,ans[i].y] <> 0 then
70       writeln(ans[i].x,' ',ans[i].y);
71 end;
72 begin
73   init;
74   prim;
75   print;
76   //read(n);
77 end.