new file mode 100644
--- /dev/null
+++ b/sudoku.c
@@ -0,0 +1,246 @@
+/*
+ *     $Id: sudoku.c,v 1.3 2008-04-29 15:18:53 mbroeker Exp $
+ * $Source: /development/c/demos/sudoku.c,v $
+ *
+ */
+
+/* Sudoku - The Game */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <getopt.h>
+#include <string.h>
+#include <errno.h>
+#include <limits.h>
+
+#ifndef DIM
+#define DIM 9
+#endif
+
+#define COLORED "\e[31m"
+#define FGCOLOR "\e[37m"
+#define BGCOLOR "\e[40m\e[2J"
+#define   RESET "\e[0m"
+
+#define TRUE   1
+#define FALSE  0
+
+#ifndef u_int
+typedef unsigned int u_int;
+#endif
+
+#ifndef MAX_ITERATIONS
+#define MAX_ITERATIONS 10000000
+#endif
+
+struct Field {
+    u_int value;
+    int isConst;
+};
+
+/* the easiest way to get statistics */
+static unsigned long iterations = 0;
+
+typedef struct Field Field;
+typedef Field **Board;
+
+/**
+ * read nxn fields from commandline and store it in the Board variable
+ */
+int readBoard (Board board)
+{
+    int i, j;
+
+    u_int c;
+
+    for (i = 0; i < DIM; i++) {
+        for (j = 0; j < DIM; j++) {
+            if (scanf ("%u", &c) < 1) {
+                fprintf (stderr, "readBoard: Not enough elements\n");
+                fprintf (stderr, "readBoard: Got %d, needed %d\n", i * DIM + j, (DIM) * (DIM));
+                return FALSE;
+            }
+            board[i][j].value = c;
+            board[i][j].isConst = (c == 0) ? 0 : 1;
+        }
+    }
+    return TRUE;
+}
+
+/**
+ * Show the content of the Board in a human readable manner
+ */
+void showBoard (Board board, int colored)
+{
+    int i, j;
+
+    for (i = 0; i < DIM; i++) {
+        if ((i % 3) == 0)
+            printf ("\n");
+
+        for (j = 0; j < DIM; j++) {
+            if ((board[i][j].isConst && colored))
+                printf ("%s%2u%s ", COLORED, board[i][j].value, FGCOLOR);
+            else
+                printf ("%2u ", board[i][j].value);
+            if (((j + 1) % 3) == 0)
+                printf ("  ");
+        }
+        printf ("\n");
+    }
+}
+
+/**
+ * checks for the possibility of value at board[row][col]
+ */
+int check (Board board, int row, int col, u_int value)
+{
+    int i, j;
+
+    if (board[row][col].value > 0)
+        return FALSE;
+
+    for (i = 0; i < DIM; i++) {
+        /*
+         * check vertically
+         */
+        if (board[row][i].value == value)
+            return FALSE;
+        /*
+         * check horizontally
+         */
+        if (board[i][col].value == value)
+            return FALSE;
+    }
+
+    /*
+     * check block for unique values
+     */
+    for (i = row - (row % 3); i < row - (row % 3) + 3; i++)
+        for (j = col - (col % 3); j < col - (col % 3) + 3; j++)
+            if (board[i][j].value == value)
+                return FALSE;
+
+    return TRUE;
+}
+
+/**
+ * go recursive from k to DIM^2 and try to solve the puzzle
+ */
+int solveBoard (Board board, int k)
+{
+    u_int i;
+    int q;
+
+    if ((++iterations > MAX_ITERATIONS))
+        return FALSE;
+
+    while (k < (DIM) * (DIM) && (board[k / DIM][k % DIM].value != 0))
+        k++;
+
+    if (k == (DIM) * (DIM))
+        return TRUE;
+
+    for (q = FALSE, i = 1; q == FALSE && i <= 9; i++) {
+        if (check (board, k / DIM, k % DIM, i) == TRUE) {
+            board[k / DIM][k % DIM].value = i;
+            if (((DIM) * (DIM) - 1) == k)
+                q = TRUE;
+            else if ((q = solveBoard (board, k + 1)) == FALSE) {
+                board[k / DIM][k % DIM].value = 0;
+            }
+        }
+    }
+
+    return q;
+}
+
+/**
+ * Deletes every Field of the Board (CLEANUP)
+ */
+void freeBoard (const Board board)
+{
+    int i;
+
+    for (i = 0; i < DIM; i++) {
+        if (board[i] != NULL)
+            free (board[i]);
+    }
+}
+
+/**
+ * Show plain usage screen
+ */
+void usage (char *name)
+{
+    printf ("Usage: %s [-c] [-h]\n\n", name);
+    printf ("-c\t\tcolored output\n");
+    printf ("-h\t\tshows this help\n");
+    printf ("Report bugs to mbroeker@largo.homelinux.org\n");
+}
+
+int main (int argc, char **argv)
+{
+    Board b;
+    int i;
+    int ret;
+    int colored = 0;
+
+    while ((i = getopt (argc, argv, "ch")) != -1) {
+        switch (i) {
+        case 'h':
+            usage (argv[0]);
+            return EXIT_SUCCESS;
+        case 'c':
+            printf ("%s%s", BGCOLOR, FGCOLOR);
+            colored = 1;
+            break;
+        default:
+            usage (argv[0]);
+            return EXIT_FAILURE;
+        }
+    }
+
+    if ((DIM % 3) != 0) {
+        fprintf (stderr, "DIM must be a multiple of 3\n");
+        fprintf (stderr, "RECOMPILE WITH -DDIM=9\n");
+        return EXIT_FAILURE;
+    }
+
+    if ((b = calloc (DIM, sizeof (Field *))) == NULL) {
+        perror ("calloc");
+        return EXIT_FAILURE;
+    }
+
+    for (i = 0; i < DIM; i++) {
+        if ((b[i] = malloc ((DIM * sizeof (Field)) + 1)) == NULL) {
+            perror ("malloc");
+            return EXIT_FAILURE;
+        }
+    }
+
+    printf ("Sudoku - Enter a %dx%d Matrix\n", DIM, DIM);
+
+    if (readBoard (b) == FALSE) {
+        fprintf (stderr, "Input Error: Aborting\n");
+        return EXIT_FAILURE;
+    }
+
+    showBoard (b, colored);
+
+    if ((ret = solveBoard (b, 0)) == TRUE)
+        printf ("\nPuzzle solved after %lu recursions\n", iterations);
+    else
+        printf ("\nCannot solve your puzzle after %lu recursions\n", iterations);
+
+    showBoard (b, colored);
+    freeBoard (b);
+
+    if (b != NULL)
+        free (b);
+
+    if (colored)
+        printf ("%s", RESET);
+
+    return EXIT_SUCCESS;
+}