From 3568412f8f230774d0d11d7ed1c897424f95d3ef Mon Sep 17 00:00:00 2001
From: Sebastiano Tronto <sebastiano.tronto@gmail.com>
Date: Thu, 11 Nov 2021 21:37:34 +0100
Subject: Rewritten from scratch. Welocme nissy 2.0!

---
 old/2021-02-28-transformcube-works/src/utils.h | 70 ++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 old/2021-02-28-transformcube-works/src/utils.h

(limited to 'old/2021-02-28-transformcube-works/src/utils.h')

diff --git a/old/2021-02-28-transformcube-works/src/utils.h b/old/2021-02-28-transformcube-works/src/utils.h
new file mode 100644
index 0000000..4b6df8c
--- /dev/null
+++ b/old/2021-02-28-transformcube-works/src/utils.h
@@ -0,0 +1,70 @@
+/* General utility functions */
+
+#ifndef UTILS_H
+#define UTILS_H
+
+#include <stdbool.h>
+
+#define min(a,b) (((a) < (b)) ? (a) : (b))
+#define max(a,b) (((a) > (b)) ? (a) : (b))
+
+/* Some useful constants */
+#define pow2to11    2048
+#define pow2to12    4096
+#define pow3to7     2187
+#define pow3to8     6561
+#define pow12to4    20736
+#define factorial4  24
+#define factorial6  720
+#define factorial8  40320
+#define factorial12 479001600
+#define binom12on4  495
+#define binom8on4   70
+
+/* Generic utility functions */
+void swap(int *a, int *b);
+void intarrcopy(int *src, int *dst, int n);
+int sum(int *a, int n);
+bool is_perm(int *a, int n);
+bool is_perm(int *a, int n);
+
+
+/* Standard mathematical functions */
+int powint(int a, int b);
+int factorial(int n);
+int binomial(int n, int k);
+
+/* Converts the integer a to its representation in base b (first n digits
+ * only) and saves the result in r. */
+void int_to_digit_array(int a, int b, int n, int *r);
+int digit_array_to_int(int *a, int n, int b);
+
+/* Converts the first n-1 digits of a number to an array a of digits in base b;
+ * then adds one element to the array, so that the sum of the elements of a is
+ * zero modulo b.
+ * This is used for determing the edge orientation from an 11-bits integer or
+ * the corner orientation from a 7-trits integer. */
+void int_to_sum_zero_array(int x, int b, int n, int *a);
+ 
+/* Converts a permutation on [0..(n-1)] into the integer i which is the index
+ * of the permutation in the sorted list of all n! such permutations. */
+int perm_to_index(int *a, int n);
+void index_to_perm(int p, int n, int *r);
+
+/* Determine the sign of a permutation */
+int perm_sign(int a[], int n);
+
+/* Converts a k-element subset of a set from an array of n elements, of which k
+ * are 1 and n-k are 0, to its index in the sorted list of all such subsets. */
+int subset_to_index(int *a, int n, int k);
+void index_to_subset(int s, int n, int k, int *r);
+
+int ordered_subset_to_index(int *a, int n, int k);
+void index_to_ordered_subset(int s, int n, int k, int *r);
+
+void apply_permutation(int *perm, int *set, int n);
+
+/* b[i] = (a[i]+b[i])%m for i=1,...,n */
+void sum_arrays_mod(int *a, int *b, int n, int m);
+
+#endif
-- 
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