[POJ1469 COURSES]

[题目来源]Southeastern Europe 2000：

[关键字]：图论

[题目大意]：让每个学生代表一门课程，且每个课程只有一个学生代表行不行？

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[分析]：如果二分图最大匹配达到了学生数则可行否则不可行

[代码]：

View Code

 1 program Project1;
 2 var
 3   n, p, tc: longint;
 4   map: array[0..1000,0..1000] of boolean;
 5   b: array[0..1000] of boolean;
 6   link: array[0..1000] of longint;
 7 
 8 procedure init;
 9 var
10   i, j, t, y: longint;
11 begin
12   readln(p,n);
13   fillchar(map,sizeof(map),false);
14   for i := 1 to p do
15     begin
16       read(t);
17       for j := 1 to t do
18         begin
19           read(y);
20           map[i,p+y] := true;
21           map[p+y,i] := true;
22           //writeln(i,'',y);
23         end;
24     end;
25  { for i := 1 to n+p do
26     for j := 1 to n+p do writeln(i,' ',j,' ',map[i,j]); }
27 end;
28 
29 function dfs(k: longint):boolean;
30 var
31   i: longint;
32 begin
33   for i := 1 to n+p do
34     if (map[k,i]) and (not b[i]) then
35       begin
36         b[i] := true;
37         if (link[i] = 0) or (dfs(link[i])) then
38           begin
39             link[i] := k;
40             exit(true);
41           end;
42       end;
43   exit(false);
44 end;
45 
46 procedure work;
47 var
48   i, max: longint;
49 begin
50   fillchar(link,sizeof(link),0);
51   max := 0;
52   for i := 1 to p do
53     begin
54       fillchar(b,sizeof(b),false);
55       if dfs(i) then inc(max);
56     end;
57 //  writeln(max);
58 //  for i := 1 to n do write(link[i],'');
59   if max = p then writeln('YES') else writeln('NO');
60 end;
61 
62 begin
63   readln(tc);
64   while tc > 0 do
65     begin
66       init;
67       work;
68       dec(tc);
69     end;
70 end.