Pku2239 Selecting Courses

After seeing this title, I finally handed in the ctsc tree DP. The WA result is self-evident.

There are two ways to carefully read the question:

1. Split each course into two points.

(I '--> J)

(I --> J ')

The following is a problem with the largest independent set. You can subtract the number of matching points.

This idea has no practice. If there is something wrong, please point it out.

2. Many people use this method. The bipartite graph has 84 time points on one side and the course on the other side. After the edge is connected, find the maximum match.

View code

 1 program pku2239(input,output);
 2 var
 3    f  : array[0..100,0..301] of boolean;
 4    lk : array[0..301] of longint;
 5    v  : array[0..301] of boolean;
 6    n  : longint;
 7 procedure init;
 8 var
 9    i,j,x,y,z : longint;
10 begin
11    fillchar(f,sizeof(f),false);
12    fillchar(lk,sizeof(lk),0);
13    readln(n);
14    for i:=1 to n do
15    begin
16       read(x);
17       for j:=1 to x do
18       begin
19      read(y,z);
20      f[(y-1)*12+z,i]:=true;
21       end;
22       readln;
23    end;
24 end; { init }
25 function find(now :longint ):boolean;
26 var
27    i : longint;
28 begin
29    for i:=1 to n do
30       if (f[now,i])and(not v[i]) then
31       begin
32      v[i]:=true;
33      if (lk[i]=0)or(find(lk[i])) then
34      begin
35         lk[i]:=now;
36         exit(true);
37      end;
38       end;
39    exit(false);
40 end; { find }
41 function main():longint;
42 var
43    i : longint;
44 begin
45    main:=0;
46    for i:=1 to 12*7 do
47    begin
48       fillchar(v,sizeof(v),false);
49       if find(i) then
50      inc(main);
51    end;
52 end; { main }
53 begin
54    while not eof do
55    begin
56       init;
57       writeln(main);
58    end;
59 end.