A solution for Project One

/* MCS 275 Project One: random walks */

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

void walk (int m, int n);
/* executes a random walk through an mxn grid,
   prints the grid after each walk is completed */
int eccentricity (int m, int n, char a[m][n]);
/* returns the maximal |m-i-1-j| over all non blank entries
   in the mxn grid */
void print_grid (int m, int n, char a[m][n]);
/* prints the grid of points */
void move (int m, int n, char a[m][n], int *i, int *j);
/* makes one move north or east in the mxn grid, 
   starting at the current tile at position (i,j) */
int coin_toss ();
/* executes a coin toss, returns 1 or 2 */

int main(void)
{
   int m,n;
   printf("Give number of rows : ");    scanf("%d",&m);
   printf("Give number of columns : "); scanf("%d",&n);
   walk(m,n);
   return 0;
}

void walk (int m, int n)
{
   char grid[m][n];
   int c,i,j,ecc;
   int cnt = 0;
   int maxecc = 0;
   int minecc = m+n;
   c = getchar();
   while (c != 'q')
   {
      for (i = 0; i < m; ++i)         /* initialize the grid */
         for (j = 0; j < n; ++j)
            grid[i][j] = ' ';
      i = m-1;                        /* (i,j) marks position */
      j = 0;
      grid[i][j] = '+';
      while ((i != 0) || (j != n-1))  /* do the walk */
         move(m,n,grid,&i,&j);
      print_grid(m,n,grid);           /* print grid and eccentricity */
      ecc = eccentricity(m,n,grid);
      printf("Eccentricity of the walk : %d\n", ecc);
      ++cnt;                          /* update statistics */
      if (ecc > maxecc) maxecc = ecc;
      if (ecc < minecc) minecc = ecc;
      printf("Type q to quit.  Press enter to continue...");
      c = getchar();
   }
   printf("Result of %d random walks in %d-by-%d grid :\n", cnt,m,n);
   printf("  Minimal eccentricity of walks : %5d \n", minecc);
   printf("  Maximal eccentricity of walks : %5d \n", maxecc);
}

void print_grid (int m, int n, char a[m][n])
{
   int i,j;
   for (i = 0; i < m; ++i)
   {
      for (j = 0; j < n; ++j)
         putchar(a[i][j]);
      printf("\n");
   }
}

int eccentricity (int m, int n, char a[m][n])
{
   int i,j,ecc = 0;
   for (i = 0; i < m; ++i)
      for (j = 0; j < n; ++j)
         if (a[i][j] == '+')
            if (abs(m-i-j-1) > ecc)
               ecc = abs(m-i-j-1);
   return ecc;
}

int coin_toss ()
{
   int r = rand();
   if (r < RAND_MAX/2)
      return 1;
   else
      return 2;
}

void move (int m, int n, char a[m][n], int *i, int *j)
{
   int r = coin_toss();
   if ((r == 1) && (*i > 0))
      a[--*i][*j] = '+';
   else
      if (*j < n-1)
         a[*i][++*j] = '+';
}