Thread: Program that generates a "random walk" across 10*10 array

the program randomly walks through from element to element always going up, down, left, right by one element. the elements visited by the program will be labeled with the letters a through z in the order visited. If no place for a letter to go then the program terminates.

My problem is that when it reached end of row, it goes to next row and column 0 and populates. I don't want it to go out of bounds or go to next row if at end of row but don't know how to fix it. Otherwise the code works fine.

I would like some help in fixing that and after fixed, please provide some ideas to simplify the code if possible. tks

Code:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main (void) {

int i, j, k, direction;
char board[10][10];
const char letters[] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'};

srand ((unsigned) time(NULL));

for (i = 0; i < 10; i++)
  for (j = 0; j < 10; j++)
    board[i][j] = '.';

i = 0;
j = 0;    
k = 1;
board[i][j] = letters[0];
while (k < 26) {
  direction = rand() % 4;
    switch (direction) {
      case 0: if (board[i][j + 1] == '.'){
              board[i][j +1] = letters[k];  //move right 
              k++; j++;}      
              if (board[i][j + 1] != '.' && board[i + 1][j] != '.' && board[i - 1][j] != '.' && board[i][j - 1] != '.')
              k = 27;
              break;     
      case 1: if (board[i + 1][j] == '.') {
              board[i + 1][j] = letters[k];  //move down
              k++; i++; }
              if (board[i][j + 1] != '.' && board[i + 1][j] != '.' && board[i - 1][j] != '.' && board[i][j - 1] != '.')
              k = 27;
              break;
      case 2: if (board[i - 1][j] == '.'){
              board[i - 1][j] = letters[k];  //move up
              k++; i--; }
              if (board[i][j + 1] != '.' && board[i + 1][j] != '.' && board[i - 1][j] != '.' && board[i][j - 1] != '.')
              k = 27;
              break;      
      case 3: if (board[i][j - 1] == '.') {
              board[i][j - 1] = letters[k];  //move left
              k++; j--;}
              if (board[i][j + 1] != '.' && board[i + 1][j] != '.' && board[i - 1][j] != '.' && board[i][j - 1] != '.')
              k = 27;
              break;
}
}
for (i = 0; i < 10; i++) {
  for (j = 0; j < 10; j++)
    printf ("%4c", board[i][j]);
  printf ("\n");
}

return 0;

}

You can't take a step to the right if you're on the right side of the board. So, before you take a step to the right, you need to check whether you are, in fact, on the right side of the board. If you are, you need to choose a different direction. You'll also need to adjust your "help I'm blocked in" test to take this into account as well.

it's still not working....I just don't understand how let's say array[0][9] becomes array[[1][0] or array[4][0] becomes array[3][9]?????????

i modified to look like this with no success

Code:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#define ROWS 10
#define COLS 10
int main (void) {

int i, j, k, direction;
char board[ROWS][COLS];
const char letters[] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'};

srand ((unsigned) time(NULL));

for (i = 0; i < ROWS; i++)
  for (j = 0; j < COLS; j++)
    board[i][j] = '.';

i = 0;
j = 0;    
k = 1;
board[i][j] = letters[0];
while (k < 26) {
  direction = rand() % 4;
    switch (direction) {
      case 0: if (board[i][j + 1] == '.' && i != ROWS - 1){
              board[i][j +1] = letters[k];  //move right 
              k++; j++;}      
              if (board[i][j + 1] != '.' && board[i + 1][j] != '.' && board[i - 1][j] != '.' && board[i][j - 1] != '.')
              k = 27;
              break;     
      case 1: if (board[i + 1][j] == '.' && j != COLS -1) {
              board[i + 1][j] = letters[k];  //move down
              k++; i++; }
              if (board[i][j + 1] != '.' && board[i + 1][j] != '.' && board[i - 1][j] != '.' && board[i][j - 1] != '.')
              k = 27;
              break;
      case 2: if (board[i - 1][j] == '.' && j != 0){
              board[i - 1][j] = letters[k];  //move up
              k++; i--; }
              if (board[i][j + 1] != '.' && board[i + 1][j] != '.' && board[i - 1][j] != '.' && board[i][j - 1] != '.')
              k = 27;
              break;      
      case 3: if (board[i][j - 1] == '.' && i != 0) {
              board[i][j - 1] = letters[k];  //move left
              k++; j--;}
              if (board[i][j + 1] != '.' && board[i + 1][j] != '.' && board[i - 1][j] != '.' && board[i][j - 1] != '.')
              k = 27;
              break;
}
}
for (i = 0; i < ROWS; i++) {
  for (j = 0; j < COLS; j++)
    printf ("%4c", board[i][j]);
  printf ("\n");
}

return 0;

}

The same way 9 becomes 10: carry. An array is stored all in one chunk, so the end of one row is followed immediately by the beginning of the next.

oh yeah, i remember that it's stored in memory consecutively....forgot about that.

any suggestion to fix? Also any suggestions for improving the code?

ok. got it...THANK YOU VERY MUCH FOR THE HELP

Code:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#define ROWS 10
#define COLS 10
int main (void) {

int i, j, k, direction;
char board[ROWS][COLS];
const char letters[] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'};

srand ((unsigned) time(NULL));

for (i = 0; i < ROWS; i++)
  for (j = 0; j < COLS; j++)
    board[i][j] = '.';

i = 0;
j = 0;    
k = 1;
board[i][j] = letters[0];
while (k < 26) {
  direction = rand() % 4;
    switch (direction) {
      case 0: if (board[i][j + 1] == '.' && j != ROWS - 1){
              board[i][j +1] = letters[k];  //move right 
              k++; j++;}      
              if (board[i][j + 1] != '.' && board[i + 1][j] != '.' && board[i - 1][j] != '.' && board[i][j - 1] != '.')
              k = 27;
              break;     
      case 1: if (board[i + 1][j] == '.' && i != COLS -1) {
              board[i + 1][j] = letters[k];  //move down
              k++; i++; }
              if (board[i][j + 1] != '.' && board[i + 1][j] != '.' && board[i - 1][j] != '.' && board[i][j - 1] != '.')
              k = 27;
              break;
      case 2: if (board[i - 1][j] == '.' && i != 0){
              board[i - 1][j] = letters[k];  //move up
              k++; i--; }
              if (board[i][j + 1] != '.' && board[i + 1][j] != '.' && board[i - 1][j] != '.' && board[i][j - 1] != '.')
              k = 27;
              break;      
      case 3: if (board[i][j - 1] == '.' && j != 0) {
              board[i][j - 1] = letters[k];  //move left
              k++; j--;}
              if (board[i][j + 1] != '.' && board[i + 1][j] != '.' && board[i - 1][j] != '.' && board[i][j - 1] != '.')
              k = 27;
              break;
}
}
for (i = 0; i < ROWS; i++) {
  for (j = 0; j < COLS; j++)
    printf ("%4c", board[i][j]);
  printf ("\n");
}

return 0;

}

CAN I GET SOME HELP WITH IMPROVING THE CODE? ANY SUGGESTIONS?

in improving code i mean making it shorter and more to the point if possible

oh yeah, one last question.....when i wanna break out of the switch loop, i used k = 27; .... is there a different or better way to break out of that while loop? Also, if you run this code, it works 9 out of 10 times but sometimes nothing happens when i run it, must be something wrong somewhere

ok. goto works well and i like it better.....this code hangs 1 in 20 times, any reason why?