+static int
+compare_int(const void *a_, const void *b_)
+{
+ const int *a = a_;
+ const int *b = b_;
+ return *a < *b ? -1 : *a > *b;
+}
+
+static void
+check_permutation(int *a, int n, const char *name)
+{
+ int b[n];
+ memcpy(b, a, n * sizeof *a);
+ qsort(b, n, sizeof *b, compare_int);
+ for (int i = 0; i < n; i++)
+ if (b[i] != i)
+ {
+ fprintf(stderr, "bad %s permutation:", name);
+ for (int i = 0; i < n; i++)
+ fprintf(stderr, " %d", a[i]);
+ putc('\n', stderr);
+ exit(1);
+ }
+}
+