kruskal最小生成树(Pascal版)

 1 const maxn=1050;maxm=100050;
 2 type
 3         edge=record
 4                 f,g,w:longint;
 5         end;
 6 var
 7         i,j,k,l,m,n,tot:longint;
 8         c:array[0..maxn] of longint;
 9         a:array[0..maxm] of edge;
10 function getfat(x:longint):longint;
11         begin
12                 if c[x]<>x then c[x]:=getfat(c[x]);
13                 exit(c[x]);
14         end;
15 operator <(e1,e2:edge)x:boolean;   //为了便于排序，重载运算符
16         begin
17                 x:=e1.w<e2.w;
18         end;
19 operator >(e1,e2:edge)x:boolean;
20         begin
21                 x:=e1.w>e2.w;
22         end;
23 procedure swap(var e1,e2:edge);
24         var e3:edge;
25         begin
26                 e3:=e1;e1:=e2;e2:=e3;
27         end;
28 procedure sort(l,r:longint);
29         var
30                 i,j:longint;
31                 x:edge;
32         begin
33                 i:=l;j:=r;x:=a[(l+r) div 2];
34                 repeat
35                         while a[i]<x do inc(i);
36                         while x<a[j] do dec(j);
37                         if i<=j then
38                                 begin
39                                         swap(a[i],a[j]);
40                                         inc(i);dec(j);
41                                 end;
42                 until i>j;
43                 if l<j then sort(l,j);
44                 if i<r then sort(i,r);
45         end;
46 function newedge(x,y,z:longint):edge;
47         var e1:edge;
48         begin
49                 e1.f:=x;e1.g:=y;e1.w:=z;
50                 exit(e1);
51         end;
52 begin
53         readln(n,m);
54         for i:=1 to n do c[i]:=i;
55         for i:=1 to m do
56                 begin
57                         readln(j,k,l);
58                         a[i]:=newedge(j,k,l);
59                 end;
60         sort(1,m);
61         j:=1;tot:=0;
62         for i:=1 to n-1 do
63                 begin
64                         repeat
65                                 k:=getfat(a[j].f);   //并查集判定
66                                 l:=getfat(a[j].g);
67                                 if k<>l then break;
68                                 inc(j);
69                         until j>m;
70                         if j>m then break;    //无法连通
71                         c[k]:=l;tot:=tot+a[j].w;
72                 end;
73         if j>m then writeln(-1) else writeln(tot);
74 end.