permutation: Generate permutations of arrays

[ccan] / ccan / permutation / _info

diff --git a/ccan/permutation/_info b/ccan/permutation/_info
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+#include "config.h"
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+/**
+ * permutation - Generate permutations
+ *
+ * This module allows you to generate all permutations of a given
+ * number of elements.  It can also modify a user-supplied array in
+ * place through all those permutations.
+ *
+ * It uses the "plain changes" method, aka the
+ * Steinhaus-Johnson-Trotter algorithm to generate the permtations.
+ * This has some advantages over a naive recursive algorithm:
+ *
+ * - Each permutation is generated from the last by a single swap of
+ *   adjacent elements
+ *
+ * - Constructing each permutation in place from the last takes
+ *   amortized O(1) time.
+ *
+ * License: LGPL (v2.1 or any later version)
+ * Example:
+ *     // Given "1 2 3" outputs 1 2 3 1 3 2 3 1 2 3 2 1 2 3 1 2 1 3
+ *     #include <stdio.h>
+ *     #include <ccan/permutation/permutation.h>
+ *
+ *     int main(int argc, char *argv[])
+ *     {
+ *             int i;
+ *             struct permutation *pi = permutation_new(argc - 1);
+ *
+ *             do {
+ *                     for (i = 1; i < argc; i++)
+ *                             printf("%s ", argv[i]);
+ *                     printf("\n");
+ *             } while (permutation_change_array(pi,
+ *                      &argv[1], sizeof(argv[1])));
+ *             exit(0);
+ *     }
+ */
+int main(int argc, char *argv[])
+{
+       /* Expect exactly one argument */
+       if (argc != 2)
+               return 1;
+
+       if (strcmp(argv[1], "depends") == 0) {
+               printf("ccan/build_assert\n");
+               printf("ccan/mem\n");
+               return 0;
+       }
+
+       if (strcmp(argv[1], "testdepends") == 0) {
+               printf("ccan/array_size\n");
+               return 0;
+       }
+
+       return 1;
+}