搜索 B
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Description
Background
The knight is getting bored of seeing the same black and white squares again and again and has decided to make a journey
around the world. Whenever a knight moves, it is two squares in one direction and one square perpendicular to this. The world of a knight is the chessboard he is living on. Our knight lives on a chessboard that has a smaller area than a regular 8 * 8 board, but it is still rectangular. Can you help this adventurous knight to make travel plans?
Problem
Find a path such that the knight visits every square once. The knight can start and end on any square of the board.
The knight is getting bored of seeing the same black and white squares again and again and has decided to make a journey
around the world. Whenever a knight moves, it is two squares in one direction and one square perpendicular to this. The world of a knight is the chessboard he is living on. Our knight lives on a chessboard that has a smaller area than a regular 8 * 8 board, but it is still rectangular. Can you help this adventurous knight to make travel plans?
Problem
Find a path such that the knight visits every square once. The knight can start and end on any square of the board.
Input
The input begins with a positive integer n in the first line. The following lines contain n test cases. Each test case consists of a single line with two positive integers p and q, such that 1 <= p * q <= 26. This represents a p * q chessboard, where p describes how many different square numbers 1, . . . , p exist, q describes how many different square letters exist. These are the first q letters of the Latin alphabet: A, . . .
Output
The output for every scenario begins with a line containing "Scenario #i:", where i is the number of the scenario starting at 1. Then print a single line containing the lexicographically first path that visits all squares of the chessboard with knight moves followed by an empty line. The path should be given on a single line by concatenating the names of the visited squares. Each square name consists of a capital letter followed by a number.
If no such path exist, you should output impossible on a single line.
If no such path exist, you should output impossible on a single line.
Sample Input
31 12 34 3
Sample Output
Scenario #1:A1Scenario #2:impossibleScenario #3:
A1B3C1A2B4C2A3B1C3A4B2C4
代码:
#include <stdio.h>#include <stdlib.h>
#define MAX 27
int map[MAX][MAX], sx[MAX], sy[MAX];int dir[8][2] = {{-2, -1}, {-2, 1}, {-1, -2}, {-1, 2},{1, -2}, {1, 2}, {2, -1}, {2, 1}};int p, q, sign, step;
void dfs(int i, int j){ if (sign) return; int x, y, k; step++; sx[step] = i; sy[step] = j; if(step == p * q) { sign = 1; return; } map[i][j] = 1; for (k = 0; k < 8; k++) { y = j + dir[k][0]; x = i + dir[k][1]; if (map[x][y] == 0 && x > 0 && x <= p && y > 0 && y <= q) { dfs(x, y); step--; } } map[i][j] = 0;}
int main(){ int i, j, n, t = 0; scanf("%d", &n); while(n--) { sign = 0; step = 0; t++; scanf("%d%d", &p, &q); for (i = 1; i <= p; i++) { for(j = 1; j <= q; j++) { map[i][j] = 0; } } dfs(1, 1); printf("Scenario #%d:\n", t); if (sign) { for (i = 1; i <= p * q; i++) { printf("%c%d", sy[i] + 64, sx[i]); } printf("\n"); } else { printf("impossible\n"); }
if (n != 0) printf("\n"); }
return 0;}
分析:
1、题目要求以"lexicographically"方式输出,也就是字典序...一开始没看懂这个词结果WA了N次...要以字典序输出路径,那么方向数组就要以特殊的顺序排列了...这样只要每次从dfs(1,1)开始搜索,第一个成功遍历的路径一定是以字典序排列...
2、国际象棋的棋盘,横行为字母,表示横行坐标的是y;纵行为数字,表示纵行的坐标是x...一开始又搞反了...
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