my_odd_even_sort.c

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

const int RMAX = 100;

void Usage(char* prog_name);
void Get_args(int argc, char* argv[], int* n_p, char* g_i_p);
void Generate_list(int a[], int n);
void Print_list(int a[], int n, char* title);
void Read_list(int a[], int n);
void Odd_even_sort(int a[], int n);

/*-----------------------------------------------------------------*/
int main(int argc, char* argv[]) {
   int  n;
   char g_i;
   int* a;

   Get_args(argc, argv, &n, &g_i);
   a = (int*) malloc(n*sizeof(int));
   if (g_i == 'g') {
      Generate_list(a, n);
      Print_list(a, n, "Before sort");
   } else {
      Read_list(a, n);
   }

   Odd_even_sort(a, n);

   Print_list(a, n, "After sort");
   
   free(a);
   return 0;
}  /* main */


void Usage(char* prog_name) {
   fprintf(stderr, "usage:   %s <n> <g|i>\n", prog_name);
   fprintf(stderr, "   n:   number of elements in list\n");
   fprintf(stderr, "  'g':  generate list using a random number generator\n");
   fprintf(stderr, "  'i':  user input list\n");
}  /* Usage */

void Get_args(int argc, char* argv[], int* n_p, char* g_i_p) {
   if (argc != 3 ) {
      Usage(argv[0]);
      exit(0);
   }
   *n_p = atoi(argv[1]);
   *g_i_p = argv[2][0];

   if (*n_p <= 0 || (*g_i_p != 'g' && *g_i_p != 'i') ) {
      Usage(argv[0]);
      exit(0);
   }
}  /* Get_args */

void Generate_list(int a[], int n) {
   int i;

   srandom(0);
   for (i = 0; i < n; i++)
      a[i] = random() % RMAX;
}  /* Generate_list */

void Print_list(int a[], int n, char* title) {
   int i;

   printf("%s:\n", title);
   for (i = 0; i < n; i++)
      printf("%d ", a[i]);
   printf("\n\n");
}  /* Print_list */

void Read_list(int a[], int n) {
   int i;

   printf("Please enter the elements of the list\n");
   for (i = 0; i < n; i++)
      scanf("%d", &a[i]);
}  /* Read_list */

void Odd_even_sort(
      int  a[]  /* in/out */, 
      int  n    /* in     */) {
   int phase, i, temp;

   for (phase = 0; phase < n; phase++) 
      if (phase % 2 == 0) { /* Even phase */
         for (i = 1; i < n; i += 2) 
            if (a[i-1] > a[i]) {
               temp = a[i];
               a[i] = a[i-1];
               a[i-1] = temp;
            }
      } else { /* Odd phase */
         for (i = 1; i < n-1; i += 2)
            if (a[i] > a[i+1]) {
               temp = a[i];
               a[i] = a[i+1];
               a[i+1] = temp;
            }
      }
}  /* Odd_even_sort */