POJ2488 A Knight's Journey(深搜DFS,字典序,骑士游历问题)
2017-01-07 17:35
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题目:
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思路:
这道题的坑点在于字典序,一定要按照字典序进行搜索
代码;
A Knight's Journey
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. 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. Sample Input 3 1 1 2 3 4 3 Sample Output Scenario #1: A1 Scenario #2: impossible Scenario #3: A1B3C1A2B4C2A3B1C3A4B2C4 Source TUD Programming Contest 2005, Darmstadt, Germany |
[Discuss]
思路:
这道题的坑点在于字典序,一定要按照字典序进行搜索
代码;
#include <stdio.h> #include <string.h> #include <iostream> #include <stack> #include <queue> #include <vector> #include <cmath> #include <algorithm> #define mem(a,b) memset(a,b,sizeof(a)) using namespace std; int go[8][2]= {{-1,-2},{1,-2},{-2,-1},{2,-1},{-2,1},{2,1},{-1,2},{1,2}};//字典序方向 int vis[30][30]; int n,m,fl ea16 ag; struct node { int x,y; } a[30]; //存储每一步的坐标 void dfs(int x,int y,int step) { a[step].x=x,a[step].y=y;//把当前路径存入结构体 if(step==n*m)//搜完每一个格子打印路径 { for(int i=1; i<=step; i++) printf("%c%d",a[i].y-1+'A',a[i].x);//打印路径 printf("\n"); flag=1; } if(flag)return; for(int i=0; i<8; i++) { int xx=x+go[i][0]; int yy=y+go[i][1]; if(xx>0&&xx<=n&&yy>0&&yy<=m&&vis[xx][yy]==0)//判断是否越界 { vis[xx][yy]=1;//搜过的标记 dfs(xx,yy,step+1); vis[xx][yy]=0;//标记回来 } } } int main() { int t,ci=1; scanf("%d",&t); while(t--) { mem(vis,0); flag=0; scanf("%d%d",&n,&m); printf("Scenario #%d:\n",ci++); vis[1][1]=1;//先把第一个坐标标记了 dfs(1,1,1);//从(1,1)开始搜索 if(flag==0)printf("impossible\n"); printf("\n"); } return 0; }
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