[TYVJ1307 联络员]

【题目】:联络员

【来源】:Tyvj1307

【关键字】:图论 必连边

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【分析】:克鲁斯卡尔,先将必连边加入生成树中,再用剩下的边构建生成树.也可以先将必连边的全加入答案,然后改为零.在对所有边找最小生成树.

【小结】:_______________________________________________________

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【代码】:

View Code

  1 program project1;
  2 type
  3   rec = record
  4     x, y, d: longint;
  5   end;
  6 var
  7   n, m, ans, tot, t, k: longint;
  8   e: array[0..10010] of rec;
  9   f: array[0..2010] of longint;
 10   //a: array[0..2010,0..2010,1..2] of longint;
 11 function get(k: longint):longint;
 12 begin
 13   if f[k] = k then exit(k);
 14   f[k] := get(f[k]);
 15   get := f[k];
 16 end;
 17 procedure init;
 18 var
 19   i, p, x, y, d, xx, yy: longint;
 20 begin
 21   readln(n,m);
 22   tot := 0;
 23   for i := 1 to n do f[i] := i;
 24   for i := 1 to m do
 25     begin
 26       readln(p,x,y,d);
 27       case p of
 28         1:begin
 29             inc(ans,d);
 30             xx := get(x);
 31             yy := get(y);
 32             if xx <> yy then
 33               begin
 34                 f[xx] := yy;
 35                 inc(t);
 36               end;
 37           end;
 38         2:begin
 39             inc(tot);
 40             e[tot].x := x;
 41             e[tot].y := y;
 42             e[tot].d := d;
 43           end;
 44       end;
 45     end;
 46   //for i := 1 to tot do writeln(e[i].x,' ',e[i].y,' ',e[i].d);
 47   //readln(k);
 48 end;
 49 procedure qs(l, r: longint);
 50 var
 51   i, j, mid: longint;
 52   t: rec;
 53 begin
 54   i := l;
 55   j := r;
 56   mid := e[(l+r) div 2].d;
 57   repeat
 58     while e[i].d < mid do inc(i);
 59     while e[j].d > mid do dec(j);
 60     if i <= j then
 61       begin
 62         t := e[i];
 63         e[i] := e[j];
 64         e[j] := t;
 65         inc(i);
 66         dec(j);
 67       end;
 68   until i > j;
 69   if l < j then qs(l,j);
 70   if i < r then qs(i,r);
 71 end;
 72 procedure kurs;
 73 var
 74   i, x, y: longint;
 75 begin
 76   //for i := 1 to tot do writeln(e[i].x,' ',e[i].y,' ',e[i].d);
 77  // read(k);
 78   i := 1;
 79   while t < n-1 do
 80     begin
 81       x := get(e[i].x);
 82       //writeln(x);
 83       //readln(k);
 84       y := get(e[i].y);
 85       //writeln(y);
 86       //readln(k);
 87       if x <> y then
 88         begin
 89           inc(ans,e[i].d);
 90           f[x] := y;
 91           inc(t);
 92         end;
 93       inc(i);
 94     end;
 95 end;
 96 begin
 97   init;
 98   //writeln(tot);
 99   qs(1,tot);
100   kurs;
101   writeln(ans);
102   //read(k);
103 end.