poj 2446 Chessboard (二分图利用奇偶性匹配)

Alice and Bob often play games on chessboard. One day, Alice draws a board with size M * N. She wants Bob to use a lot of cards with size 1 * 2 to cover the board. However, she thinks it too easy to bob, so she makes some holes on the board (as shown in the figure below). 

We call a grid, which doesn’t contain a hole, a normal grid. Bob has to follow the rules below: 
1. Any normal grid should be covered with exactly one card. 
2. One card should cover exactly 2 normal adjacent grids. 

Some examples are given in the figures below: 
 
A VALID solution.
 
An invalid solution, because the hole of red color is covered with a card.
 
An invalid solution, because there exists a grid, which is not covered.
Your task is to help Bob to decide whether or not the chessboard can be covered according to the rules above.

There are 3 integers in the first line: m, n, k (0 < m, n <= 32, 0 <= K < m * n), the number of rows, column and holes. In the next k lines, there is a pair of integers (x, y) in each line, which represents a hole in the y-th row, the x-th column.

If the board can be covered, output "YES". Otherwise, output "NO".

4 3 2
2 1
3 3

YES

 
A possible solution for the sample input.

！！
                    continue;
                memset(mark,0,sizeof(mark));
                ans+=find(i*m+j);
            }
        }
        //printf("%d
",ans);
        if(ans*2==n*m-k)
            printf("YES
");
        else
            printf("NO
");
    }
    return 0;
}