Data commit

Task/Curzon-numbers/C/curzon-numbers.c

@@ -0,0 +1,41 @@
+#include <stdio.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <locale.h>
+
+uint64_t modPow(uint64_t base, uint64_t exp, uint64_t mod) {
+    if (mod == 1) return 0;
+    uint64_t result = 1;
+    base %= mod;
+    for (; exp > 0; exp >>= 1) {
+        if ((exp & 1) == 1) result = (result * base) % mod;
+        base = (base * base) % mod;
+    }
+    return result;
+}
+
+bool isCurzon(uint64_t n, uint64_t k) {
+    const uint64_t r = k * n;
+    return modPow(k, n, r+1) == r;
+}
+
+int main() {
+    uint64_t k, n, count;
+    setlocale(LC_NUMERIC, "");
+    for (k = 2; k <= 10; k += 2) {
+        printf("Curzon numbers with base %ld:\n", k);
+        for (n = 1, count = 0; count < 50; ++n) {
+            if (isCurzon(n, k)) {
+                printf("%4ld ", n);
+                if (++count % 10 == 0) printf("\n");
+            }
+        }
+        for (;;) {
+            if (isCurzon(n, k)) ++count;
+            if (count == 1000) break;
+            ++n;
+        }
+        printf("1,000th Curzon number with base %ld: %'ld\n\n", k, n);
+    }
+    return 0;
+}