Generate a "random walk" across a 10x10 array

thunderchic5 · #1 21-Feb-2008, 12:16

Help! I can't seem to figure this program out and I've been working on it for over 7 hours! If you could take a look, that would be wonderful!

Problem 13 from the book is: Write a program that generate a "random walk" across a 10x10 array. The array will contain characters
(all ' . ' initially). The program must randomly "walk" from element to element, always going up, down, left, right by one element. The elements
visited by the program will be labelled with the letters A through Z, in the order visited. Here's an example:

Code:

A  .  .  .  .  .  .  .  .  .
B C D  .  .  .  .  .  .  .
.  F  E  .  .  .  .  .  .  .
H G  .   .  .  .  .  .  .  .
I   .   .   .  .  .  .  .  .  .
J   .   .  .  .  .  .  .  .   .
K  .    . R S T U V Y .
L  M P Q  .  .  . W X  .
.   N O  .  .  .   .  .  .   .
.   .   .   .   .   .  .  .  .  .

This is what I have so far:

CPP / C++ / C Code:

# include <stdio.h>
# include <time.h>
# define TRUE 1
# define FALSE 0

time_t seed;

main()
{
seed = time(NULL);
srand(seed);

char grid[10][10];
char currentchar = 'A';

int i, j, r, loop, row, col;
for (i=0; i<10; i++) {
	for (j=0; j<10; j++) {
		grid[i][j]='.';
		grid[0][0]='A';
		printf("%c", grid[i][j]);
	}
	printf("\n");
}
printf("\n");

loop=1;
i=0; j=0;
row=i; col=j;
printf("%d %d, %d %d\n", i, j, row, col);
while (loop==1) {

for (;;) {
	r = rand()%4;
	printf("%d , %d %d\n", r, row, col);
	if (currentchar == 'Z') {
		printf("Zdone!\n"); loop = 0; break;
	}
	else if ((((j-1) > -1) && grid[i][j-1] != '.' || grid[i][j-1] < currentchar) && (((i-10) > -1) && grid[i-10][j] != '.' || grid[i-10][j] < currentchar) && (((j+1) < 10) && grid[i][j+1] != '.' || grid[i][j+1] < currentchar) && (((i+10) < 100) && grid[i+10][j] != '.' || grid[i+10][j] < currentchar)) {
		loop = 0; break;
	}
	else if ((((j-1) > -1) && grid[i][j-1] != '.' || grid[i][j-1] < currentchar) && (((i-10) > -1) && grid[i-10][j] != '.' || grid[i-10][j] < currentchar) && (((j+1) < 10) && grid[i][j+1] != '.' || grid[i][j+1] < currentchar)) {
		r = 3;
	}
	else if ((((j-1) > -1) && grid[i][j-1] != '.' || grid[i][j-1] < currentchar) && (((i-10) > -1) && grid[i-10][j] != '.' || grid[i-10][j] < currentchar)) {
		r = rand()%2;
	}
	else if ((((j-1) > -1) && grid[i][j-1] != '.' || grid[i][j-1] < currentchar)) {
		r = rand()%3;
	}

	if (r == 0) {
		printf("This is 0) %d %d\n", i, j);
		if (((j-1) > -1) && grid[i][j-1] == '.') {
		printf("ye!0");
			row=i; col=(j-1);
			printf("%d %d %d %d\n", i, j, row, col);
			grid[row][col] = currentchar++;
			for (i=0; i<10; i++) {
				for (j=0; j<10; j++) {
					grid[i][j]='.';	
					grid[row][col] = currentchar;	
					printf("%c", grid[i][j]);
				}
				printf("\n");
			}
			printf("\n");
		}
		else i=row; j=col; continue;
	}
	if (r == 1) {
		printf("This is 1) %d %d\n", i, j);
		if (((i-10) > -1) && grid[i-10][j] == '.') {
		printf("ye!1");
			row=(i-10); col=(j);
			printf("%d %d %d %d\n", i, j, row, col);
			grid[row][col] = currentchar++;
			for (i=0; i<10; i++) {
				for (j=0; j<10; j++) {
					grid[i][j]='.';	
					grid[row][col] = currentchar;	
					printf("%c", grid[i][j]);
				}
				printf("\n");
			}
			printf("\n");
		}
		else i=row; j=col; continue;
	}
	if (r == 2) {
		printf("This is 2) %d %d\n", i, j);
		if (((j+1) < 10) && grid[i][j+1] == '.') {
		printf("ye!2");
			row=i; col=(j+1);
			printf("%d %d %d %d\n", i, j, row, col);
			grid[row][col] = currentchar++;
			for (i=0; i<10; i++) {
				for (j=0; j<10; j++) {
					grid[i][j]='.';	
					grid[row][col] = currentchar;	
					printf("%c", grid[i][j]);
				}
				printf("\n");
			}
			printf("\n");
		}
		else i=row; j=col; continue;
	}
	if (r == 3) {
		printf("This is 3) %d %d\n", i, j);
		if (((i+10) < 100) && grid[i+10][j] == '.') {
		printf("ye!3");
			row=(i+10); col=(j);
			printf("%d %d %d %d\n", i, j, row, col);
			grid[row][col] = currentchar++;
			for (i=0; i<10; i++) {
				for (j=0; j<10; j++) {
					grid[i][j]='.';	
					grid[row][col] = currentchar;	
					printf("%c", grid[i][j]);
				}
				printf("\n");
			}
			printf("\n");
		}
		else i=row; j=col; continue;
	}
}
}
}

fakepoo · #2 21-Feb-2008, 12:48

Looks like fun. Is there a specific question or something that you're stuck on? Also, please use C tags around your code. I refuse to read through it as is.

davekw7x · #3 21-Feb-2008, 14:43

Quote:

Originally Posted by thunderchic5

Help! I can't seem to figure this program out ...

We define a grid in terms of rows and columns: an array[rows][cols]
of chars.

We arbitrarily define row zero to be the "top" edge, column zero is the "left" edge, etc.

A move in the "down" direction is accomplished by incrementing the current row index. Moving "right" means incrementing the column
index. Etc.

Given a grid and a starting row and column mumber and a character that has been placed there, here's the logic that I might think about:

Code:

While the character is less than or equal to 'Z' and a move is possible 
Begin the big loop
    Set a variable "moved" to zero to indicate that no move has been made.
    While the value of the variable "moved" is equal to zero
    Begin the "move" loop
        Get a random direction (left, right, up, down)
        If it is possible to move in that direction, then
        Begin the If stuff
            change the current row or column index in the indicated direction
            place the character.
            increment the character.
            Set the variable "moved" to one to indicate that a move was made.
        End of the If stuff.
    End of the "move" loop.
End of the big loop.

There are two ways to leave the big loop:

Success is indicated by the fact that the character has been incremented to one more than 'Z'

If the loop quit early because of a dead end, the values of row and column can be used to tell the user where the last character was placed.

Now, looking at that orginization, what do we need?

1. Decide on what direction is indicated by numbers 0, 1, 2, 3. You can simply #define LEFT to be 0, UP to be 1, etc. (in any order that you want). A neat thing from a program point of view might be to use enums if you have had them. (Don't worry if you haven't; just use integer values.)

2. You need to know how to figure whether you can move in any given direction:

For example, given position (row, col) you can move left if (and only if)
(row > 0) and (grid[row-1][col] == '.'). Figure out and write down the other possible moves.

Simply "or"ing together the return values of the four directional move functions tells us whether any move is possible (the thing you need for the big loop).

In order to keep from having long drawn-out, easy-to-screw-up logic expressions, I would probably make functions for the possible moves:

CPP / C++ / C Code:

int can_move_left(char g[][10], int r, int c)
{
    return (c > 0) && (g[r][c-1] == '.');
}
int can_move_right(...)
{
.
.
.
}
.
.
.
int can_move(char g[][10], int r, int c)
{
    return can_move_up   (g, r, c) || 
           can_move_down (g, r, c) || 
           can_move_right(g, r, c) ||
           can_move_left (g, r, c);
}

Regards,

Dave

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Rate This Thread
Rate This Thread:

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Two-Tier data dissemination code installation problem	nidhibansal1984	Computer Software Forum - Linux	6	16-Sep-2007 10:13
Text-Based Roulette Game	mfm1983	C++ Forum	5	29-Nov-2006 12:20
BOOKEEPING program, HELP!!	yabud	C Programming Language	10	17-Nov-2006 03:48
Pipeline freeze simulation	darklightred	C++ Forum	6	27-Jul-2006 19:37
How to read particular memory location ?	realnapster	C Programming Language	10	10-May-2006 09:11

Generate a "random walk" across a 10x10 array

Re: walk.c program ECS 30 help!

Re: walk.c program ECS 30 help!