Another solution using Bignum support.

16/euler16.cpp

@@ -0,0 +1,26 @@
+// This solution needs the GNU MP Bignum library
+// g++ euler16.cpp -o euler16 -lgmpxx -lgmp
+
+#include <gmpxx.h>
+#include <cmath>
+#include <vector>
+#include <iostream>
+
+int main(void) {
+    mpz_class power = 1;
+    mpz_class modulo = 0;
+    mpz_class tens = 10;
+    mpz_class digitsum = 0;
+
+    for (int i = 1; i <= 1000; ++i) {
+        power *= 2;
+    }
+
+    while (power != 0) {
+        digitsum = digitsum + power % tens;
+        power = power / 10;
+    }
+
+    std::cout << digitsum << std::endl;
+    return EXIT_SUCCESS;
+}