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/* List manipulations */
#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
struct list { int hd; struct list * tl; };
struct list * buildlist(int n)
{
struct list * r;
if (n < 0) return NULL;
r = malloc(sizeof(struct list));
r->hd = n;
r->tl = buildlist(n - 1);
return r;
}
struct list * reverselist (struct list * l)
{
struct list * r, * r2;
for (r = NULL; l != NULL; l = l->tl) {
r2 = malloc(sizeof(struct list));
r2->hd = l->hd;
r2->tl = r;
r = r2;
}
return r;
}
struct list * reverse_inplace(struct list * l)
{
struct list * prev, * next;
prev = NULL;
while (l != NULL) {
next = l->tl;
l->tl = prev;
prev = l;
l = next;
}
return prev;
}
int checklist(int n, struct list * l)
{
int i;
for (i = 0; i <= n; i++) {
if (l == NULL) return 0;
if (l->hd != i) return 0;
l = l->tl;
}
return (l == NULL);
}
int main(int argc, char ** argv)
{
int n, niter, i;
struct list * l;
if (argc >= 2) n = atoi(argv[1]); else n = 1000;
if (argc >= 3) niter = atoi(argv[1]); else niter = 100000;
l = buildlist(n);
if (checklist(n, reverselist(l))) {
printf("OK\n");
} else {
printf("Bug!\n");
return 2;
}
for (i = 0; i < 2*niter + 1; i++) {
l = reverse_inplace(l);
}
if (checklist(n, l)) {
printf("OK\n");
} else {
printf("Bug!\n");
return 2;
}
return 0;
}
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