Problem 40

40.c

@@ -0,0 +1,26 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+int champernowneDigit (int n) {
+    int d = 1;
+    int next = 9;
+    while (n > next) {
+        n -= next;
+        next = 9 * ++d * (int) pow (10, d - 1);
+    }
+
+    for (int k = 1; k <= d; k++) {
+        if ((n - k) % d == 0) {
+            return (((n - k) / (d * (int) pow (10, d - k))) % 10) + (k == 1 ? 1 : 0);
+        }
+    }
+}
+
+int main () {
+    int product = 1;
+    for (int i = 1; i <= 1000000; i *= 10) {
+        product *= champernowneDigit (i);
+    }
+    printf ("%d\n", product);
+}