poj 1573 Robot Motion 【模擬】【刷題計劃】

 

Robot Motion

Time Limit: 1000MS		Memory Limit: 10000K
Total Submissions: 14641		Accepted: 7032

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 5
NEESWE
WWWESS
SNWWWW
4 5 1
SESWE
EESNW
NWEEN
EWSEN
0 0 0

Sample Output

10 step(s) to exit
3 step(s) before a loop of 8 step(s)

 

題意：在r行c列的地圖中，機器人從第一行的start列開始出發，N,S,W,E分別表示北南西東四個方向，問機器人走出地圖須要多少步，若是走不出地圖，輸出走到造成環狀的步數以及造成環狀路線的總步數。

思路：模擬機器人行走的過程，我是用了一個數組str存圖，一個數組map存步數,一開始地圖上的步數都爲0，當遇到步數不爲0 的狀況，說明造成了環狀。

（題目上明明說最多10行，我數組開爲20仍是tle，一直沒有找到問題，睡了一覺起來突然以爲題目範圍不靠譜，把數組開大之後，果真A了）

#include<stdio.h>
#include<string.h>
int main()
{
    char str[200][200];
    int map[200][200];
    int c,r,start,flag;
    int i,j;
    while(scanf("%d%d%d",&r,&c,&start),c!=0||r!=0||start!=0)
    {
        memset(str,0,sizeof(str));
        memset(map,0,sizeof(map));
        for(i = 1; i <= r; i ++)
            scanf("%s",str[i]+1);
        map[1][start] = 1;
        i = 1;
        j = start;
        flag = -2;
        while(1)
        {
            if(str[i][j] == 'N')
            {
                if(i-1 < 1)//走出地圖，flag標記爲-1 
                    flag = -1;
                else if(map[i-1][j] == 0)//步數爲0，說明沒有訪問過該處 
                {
                    map[i-1][j] = map[i][j] + 1;//步數增長 
                    --i;//位置也要改變 
                }    
                else //以上條件都不知足，說明造成環狀
                    flag = map[i-1][j];//記錄環開始的地方的步數 
            }
            else if(str[i][j] == 'S')//同上 
            {
                if(i + 1 > r)
                    flag = -1;
                else if(map[i+1][j] == 0)
                {
                    map[i+1][j] = map[i][j] + 1;
                    ++i;
                }
                else 
                    flag = map[i+1][j];
            }
            else if(str[i][j] == 'W')//同上 
            {
                if(j-1 < 1)
                    flag = -1;
                else if(map[i][j-1] == 0) 
                {
                    map[i][j-1] = map[i][j] + 1;
                    j--;
                }
                else 
                    flag = map[i][j-1];
            }
            else if(str[i][j] == 'E')//同上 
            {
                
                if(j + 1 > c)
                    flag = -1;
                else if( map[i][j+1] == 0)
                {
                    map[i][j+1] = map[i][j] + 1;
                    ++j;
                }
                else
                    flag = map[i][j+1];
            }
            if(flag != -2)//若是不爲初始值，說明已經走出地圖或者造成環 
                break;
        }
        if(flag == -1)
            printf("%d step(s) to exit\n",map[i][j]);
        else  
            printf("%d step(s) before a loop of %d step(s)\n",flag-1,map[i][j]-flag+1);
    }
    return 0;
}