[Rq 333]发明测试数据

【题目】：发明测试数据

【来源】：Rq333

【关键字】：kurscal逆推

//================================================================================================

【分析】：根据生成树的步骤,先找最小边然后判断是否在一个集合中,再加入.所以先对所有边排序,则这条边的x,y所在集合的每两个点的连边（除此边）的值最小是该边权值加一。inc(ans,(num[x]*num[y]-1)*(e[t].d+1));

【小结】：反向思维

//================================================================================================

【代码】：

View Code

 1 type
 2   rec = record
 3     x, y: longint;
 4     d: qword;
 5   end;
 6  
 7 var
 8   n: longint;
 9   ans: qword;
10   e: array[0..100010] of rec;
11   f, num: array[0..100010] of longint;
12 procedure qs(l, r: longint);
13 var
14   i, j, mid: longint;
15   t: rec;
16 begin
17   i := l;
18   j := r;
19   mid := e[(l+r) shr 1].d;
20   repeat
21     while e[i].d < mid do inc(i);
22     while e[j].d > mid do dec(j);
23     if i <= j then
24       begin
25         t := e[i];
26         e[i] := e[j];
27         e[j] := t;
28         inc(i);
29         dec(j);
30       end;
31   until i > j;
32   if l < j then qs(l,j);
33   if i < r then qs(i,r);
34 end;
35 procedure init;
36 var
37   i: longint;
38 begin
39   read(n);
40   for i := 1 to n-1 do read(e[i].x,e[i].y,e[i].d);
41   qs(1,n-1);
42   //for i := 1 to n-1 do writeln(e[i].x,' ',e[i].y,' ',e[i].d);
43 end;
44 function get(k: longint):longint;
45 begin
46   if f[k] = k then exit(k);
47   f[k] := get(f[k]);
48   get := f[k];
49 end;
50 procedure work;
51 var
52   i, x, y: longint;
53 begin
54   for i := 1 to n do f[i] := i;
55   for i := 1 to n do num[i] := 1;
56   for i := 1 to n-1 do
57     begin
58       x := get(e[i].x);
59       y := get(e[i].y);
60       ans := ans+(num[x]*num[y]-1)*(e[i].d+1)+e[i].d;
61       f[x] := y;
62       num[y] := num[x]+num[y];
63       //writeln(ans);
64     end;
65 end;
66 begin
67   init;
68   work;
69   writeln(ans);
70   //read(ans);
71 end.