poj 1573 Robot Motion——模拟（读题要认真）

Robot Motion

Time Limit: 1000MS
Memory Limit: 10000KTotal Submissions: 10231
Accepted: 4983

Description

A robot has been programmed to follow the instructions in its path. Instructions for the next direction the robot is to move are laid down in a grid. The possible instructions are 

N north (up the page) 
S south (down the page) 
E east (to the right on the page) 
W west (to the left on the page) 

For example, suppose the robot starts on the north (top) side of Grid 1 and starts south (down). The path the robot follows is shown. The robot goes through 10 instructions in the grid before leaving the grid. 

Compare what happens in Grid 2: the robot goes through 3 instructions only once, and then starts a loop through 8 instructions, and never exits. 

You are to write a program that determines how long it takes a robot to get out of the grid or how the robot loops around. 

Input

There will be one or more grids for robots to navigate. The data for each is in the following form. On the first line are three integers separated by blanks: the number of rows in the grid, the number of columns in the grid, and the number of the column in which the robot enters from the north. The possible entry columns are numbered starting with one at the left. Then come the rows of the direction instructions. Each grid will have at least one and at most 10 rows and columns of instructions. The lines of instructions contain only the characters N, S, E, or W with no blanks. The end of input is indicated by a row containing 0 0 0.

Output

For each grid in the input there is one line of output. Either the robot follows a certain number of instructions and exits the grid on any one the four sides or else the robot follows the instructions on a certain number of locations once, and then the instructions on some number of locations repeatedly. The sample input below corresponds to the two grids above and illustrates the two forms of output. The word "step" is always immediately followed by "(s)" whether or not the number before it is 1.

Sample Input

3 6 5NEESWEWWWESSSNWWWW4 5 1SESWEEESNWNWEENEWSEN0 0 0

Sample Output

10 step(s) to exit3 step(s) before a loop of 8 step(s)

Source

Mid-Central USA 1999

思路：用mp数组记录输入的字母，用bj数组来记录步数，根据bj之间的关系算出结果然后打印...

#include <stdio.h>#include <stdlib.h>#include <string.h>char mp[15][15];int bj[15][15];int a,b;void pd(char c){    if(c=='W')        b--;    else if(c=='E')        b++;    else if(c=='N')        a--;    else        a++;}//上下左右坐标的变化int main(){    int x,y,z,qa,qb,i,j,flag;    char c='\0';    while(scanf("%d%d%d%*c",&x,&y,&z),x||y||z)    {        for(i=1; i<=x; i++)        {            for(j=1; j<=y; j++)            {                scanf("%c",&mp[i][j]);            }            getchar();        }//注意：横纵坐标都是从1开始的        memset(bj,0,sizeof(bj));        a=1;        b=z;//初始化a，b        c=mp[a][b];        qa=0;        qb=0;//记录a,b的变化前的坐标        while(1)        {            if(a<1||a>x||b<1||b>y)            {                flag=1;                break;            }//如果是越界退出，标记为1            if(bj[a][b]!=0)            {                flag=2;                break;            }//如果是成环退出，标记为2            bj[a][b]=bj[qa][qb]+1;//标记数组不但用来标记，还用来记录步数            qa=a;            qb=b;//记录下a,b变化前的值            pd(c);//变化a,b            c=mp[a][b];//取改变a,b值后的char值，以便于下一次变化        }        if(flag==1)        {            printf("%d step(s) to exit\n",bj[qa][qb]);        }        if(flag==2)        {            printf("%d step(s) before a loop of %d step(s)\n",bj[a][b]-1,bj[qa][qb]-bj[a][b]+1);        }//前几次就是挂在这里，我以为是当数<=1的时候不加（s），结果都加    }    return 0;}