Now using array instead of structs.

modsim/ass2/q7.c

 #include <stdlib.h>
 #include <stdio.h>
-#include <assert.h>
 
-typedef struct rabbit {
-    unsigned short age;
-    struct rabbit *prev, *next;
-} rabbit;
+void sequence(int n, int max_age) {
+    int i, mature = 0, new[n], died = 0;
 
-rabbit *rabbits = NULL;
-int rabbit_count = 0;
-
-rabbit *rabbit_born() {
-    rabbit *r = (rabbit*) malloc(sizeof(rabbit));
-
-    if( (r->next = rabbits) )
-        rabbits->prev = r;
-
-    r->age = 0;
-    r->prev = NULL;
-    rabbits = r;
-    rabbit_count++;
-
-    return r;
-}
-
-void rabbit_die(rabbit **ptr) {
-    rabbit *r = *ptr;
-
-    if( r->prev != NULL )
-        r->prev->next = r->next;
-
-    if( r->next != NULL )
-        r->next->prev = r->prev;
-
-    if( r == rabbits )
-        rabbits = r->next;
-    else
-        *ptr = NULL;
-
-    rabbit_count--;
-    free(r);
-}
-
-void sequence(int generations, int max_age) {
-    int i;
-    rabbit *r, *next = NULL;
-
-    rabbits = rabbit_born();
+    new[0] = 1;
     printf("1");
 
-    for( i = 1; i < generations; i++ ) {
-        for( r = rabbits; r != NULL; r = next ) {
-            next = r->next;
-
-            if( r->age++ ) {
-                rabbit_born();
-
-                if( r->age == max_age )
-                    rabbit_die(&r);
-            }
-        }
+    for( i = 1; i < n; i++ ) {
+        died = i < max_age ? 0 : new[i - max_age];
+        new[i] = mature;
+        mature = mature + new[i - 1] - died;
 
-        printf(" %d", rabbit_count);
+        printf(" %d", mature + new[i]);
     }
 
     puts("");
-
-    while( rabbits )
-        rabbit_die(&rabbits);
-}
-
-void sequence_old(int n) {
-    int i, new = 1, new_new, mature = 0, died = 0;
-
-    for( i = 0; i < n; i++ ) {
-        printf("%d + %d = %d\n", mature, new, new + mature);
-
-        new_new = mature;
-        mature = mature + new - died;
-        new = new_new;
-    }
 }
 
 int main(int argc, char *argv[]) {
@@ -90,12 +26,14 @@ int main(int argc, char *argv[]) {
         return 1;
     }
 
-    generations = atoi(argv[1]);
+    max_age = generations = atoi(argv[1]);
 
-    if( argc > 2 && (max_age = atoi(argv[2])) == 1 ) {
-        puts("MAX_AGE should be at least 2 (or 0 for infinite).");
+    if( argc > 2 && (max_age = atoi(argv[2])) < 2 ) {
+        puts("MAX_AGE should be at least 2.");
         return 1;
     }
 
     sequence(generations, max_age);
+
+    return 0;
 }