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POJ 2488 A Knight's Journey (DFS)
A Knight‘s Journey
Time Limit: 1000MS | Memory Limit: 65536K | |
Total Submissions: 30656 | Accepted: 10498 |
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
Source
TUD Programming Contest 2005, Darmstadt, Germany
题目思路很清晰就是说如果能遍历整个图则打印路径,如果不行,则输出impossible
这道题按照字典序去搜索,想清楚行列关系再写,不然会WA
1 #include<cstdio> 2 #include<cstring> 3 #include<stdlib.h> 4 #include<algorithm> 5 using namespace std; 6 const int MAXN=200+10; 7 const int INF=0x3f3f3f3f; 8 int n,m,flag; 9 int vis[MAXN][MAXN],vx[MAXN],vy[MAXN];10 int dir[8][2]={{-2,-1},{-2,1},{-1,-2},{-1,2},{1,-2},{1,2},{2,-1},{2,1}};//字典序11 void DFS(int x,int y,int sum)12 {13 vx[sum]=x;//列,字母14 vy[sum]=y;//行,数字15 if(sum==n*m)16 {17 flag=1;18 return ;19 }20 for(int i=0;i<8;i++)21 {22 int xx=x+dir[i][0];23 int yy=y+dir[i][1];24 if((1<=xx&&xx<=m)&&(1<=yy&&yy<=n)&&!vis[xx][yy]&&!flag)25 {26 vis[xx][yy]=1;27 DFS(xx,yy,sum+1);28 vis[xx][yy]=0;29 }30 }31 }32 int main()33 {34 //freopen("in.txt","r",stdin);35 int kase,cnt=0;36 scanf("%d",&kase);37 while(kase--)38 {39 flag=0;40 scanf("%d %d",&n,&m);41 memset(vis,0,sizeof(vis));42 memset(vx,0,sizeof(vx));43 memset(vy,0,sizeof(vy));44 vis[1][1]=1;45 DFS(1,1,1);46 printf("Scenario #%d:\n",++cnt);47 if(flag)48 {49 for(int i=1;i<=n*m;i++)50 printf("%c%d",‘A‘+vx[i]-1,vy[i]);51 printf("\n");52 }53 else54 printf("impossible\n");55 printf("\n");56 57 }58 return 0;59 }
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