Poj 2239 Selecting Courses (binary matching)

Question link: http://poj.org/problem? Id = 2239

Description

It is well known that it is not easy to select courses in the college, for there is usually conflict among the Time of the courses. li Ming is a student who loves study every much, and at the beginning of each term, he always wants to select courses as more as possible. of course there shocould be no conflict among the courses he selects.

There are 12 classes every day, and 7 days every week. there are hundreds of courses in the College, and teaching a course needs one class each week. to give students more convenience, though teaching a course needs only one class, a course will be taught several times in a week. for example, a course may be taught both at the 7-th class on Tuesday and 12-th class on Wednesday, you showould assume th At there is no difference between the two classes, and that students can select any class to go. at the different weeks, a student can even go to different class as his wish. because there are so easy courses in the college, selecting courses is not an easy job for Li Ming. as his good friends, can you help him?

Input

The input contains several cases. for each case, the first line contains an integer N (1 <= n <= 300), the number of courses in Li Ming's college. the following n lines represent n different courses. in each line, the first number is an integer T (1 <= T <= 7*12), the different time when students can go to study the course. then come T pairs of integers p (1 <= P <= 7) and Q (1 <= q <= 12 ), which mean that the course will be taught at the Q-th class on the p-th day of a week.

Output

For each test case, output one integer, which is the maximum number of courses Li Ming can select.

Sample Input

51 1 12 1 1 2 21 2 22 3 2 3 31 3 3

Sample output

4

Source

Poj monthly, Li haoyuan

Question:

A person chooses a course in a university. The University has many courses, and the same course can appear multiple times in different days of the week. Ask him how many courses he can select at most (there cannot be conflicts in class time );

Ideas:

Figure: you only need to accumulate the course time so that the classes at the same time in different days can be differentiated, and then you can find the maximum matching number!

The Code is as follows:

# Include <cstdio> # include <cstring> # include <algorithm> # include <iostream> using namespace STD; # define maxn 517int N; int ln, RN; int G [maxn] [maxn]; int linker [maxn]; bool used [maxn]; int DFS (int l) // find the augmented path {for (INT r = 1; r <= rn; r ++) {If (G [l] [r] &! Used [R]) {// find the augmented path, reverse used [R] = true; If (linker [R] =-1 | DFS (linker [R]) {linker [R] = L; return 1 ;}} return 0 ;}int Hungary () {int res = 0; memset (linker,-1, sizeof (linker); For (int l = 1; L <= ln; l ++) {memset (used, 0, sizeof (used )); if (DFS (L) RES ++;} return res;} int main () {int n, m; int X, Y; while (~ Scanf ("% d", & N) {memset (G, 0, sizeof (g); int Maxx = 0; For (INT I = 1; I <= N; I ++) {scanf ("% d", & M); For (Int J = 1; j <= m; j ++) {scanf ("% d", & X, & Y); int TT = 12 * x + y; G [I] [TT] = 1; if (tt> Maxx) Maxx = TT ;}} Ln = N; Rn = Maxx; int ans = Hungary (); printf ("% d \ n", ANS );} return 0 ;}

Poj 2239 Selecting Courses (binary matching)