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.
OutputFor 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 0Sample Output
10 step(s) to exit 3 step(s) before a loop of 8 step(s)
水题……分情况讨论即可。
#include <stdio.h>
#include <stdlib.h>
#define MAXNUM 100
int main()
{
char grid[10][MAXNUM];
int visited[10][MAXNUM];
int row, col;
int rrow, rcol;
int walk, run;
int i, j;
while(1)
{
scanf("%d%d", &row, &col);
if(row==0 && col==0) break;
scanf("%d", &rcol);
for(i=0; i<row; i++)
{
scanf("%s", grid[i]);
for(j=0; j<col; j++)
{
visited[i][j]=0;
}
}
rcol--;
rrow=0;
walk=0;
run=0;
while(1)
{
if(rrow==-1 || rcol==-1 || rrow==row || rcol==col) break;
visited[rrow][rcol]++;
if(visited[rrow][rcol]==1) walk++;
else if(visited[rrow][rcol]==2)
{
walk--;
run++;
}
else if(visited[rrow][rcol]==3) break;
if(grid[rrow][rcol]=='N') rrow--;
else if(grid[rrow][rcol]=='S') rrow++;
else if(grid[rrow][rcol]=='E') rcol++;
else if(grid[rrow][rcol]=='W') rcol--;
}
if(run==0)
{
printf("%d step(s) to exit\n", walk);
}
else
{
printf("%d step(s) before a loop of %d step(s)\n", walk, run);
}
}
return 0;
}