| Time Limit: 1 second | |
| Memory Limit: 128 MB | |
| Description | |
| A knight moves on an N×N chessboard and must try to visit every square exactly once (no revisiting). Given the board size and the starting square, output the longest possible path. | |
| Note that this problem doesn't require a full complete path. It only asks you to find the longest path possible, and output that path. | |
| Constraints | |
| - 6 ≤ N ≤ 666 | |
| Input | |
| - The first line contains the integer N. | |
| - The second line contains two integers r c — the starting position (row and column), 1-indexed. | |
| Output | |
| - The first line of output should be an integer l: the length of the path you found(remember to include r0, c0) | |
| - Then output l lines. Each line must contain two integers r c (1-indexed), the successive positions visited by the knight, starting with the given starting position. | |
| When outputting the answer, make sure to not have an extra empty line at the end of the output after printing out the final move. | |
| - The first pair of coordinates in your path must be the starting points r0 and c0. | |
| Sample Input | |
| 6 | |
| 1 1 | |
| Sample Output | |
| 36 | |
| 1 1 | |
| 3 2 | |
| 5 1 | |
| 6 3 | |
| 5 5 | |
| 3 6 | |
| 2 4 | |
| 1 6 | |
| 3 5 | |
| 5 6 | |
| 4 4 | |
| 5 2 | |
| 3 1 | |
| 1 2 | |
| 3 3 | |
| 2 1 | |
| 1 3 | |
| 2 5 | |
| 4 6 | |
| 6 5 | |
| 5 3 | |
| 6 1 | |
| 4 2 | |
| 5 4 | |
| 6 6 | |
| 4 5 | |
| 6 4 | |
| 4 3 | |
| 6 2 | |
| 4 1 | |
| 2 2 | |
| 1 4 | |
| 2 6 | |
| 3 4 | |
| 1 5 | |
| 2 3 |