C Implementation of Problem 16

View source code here on GitHub!

Includes

• "bcd.h"

• "macros.h" (implicitly via bcd.h)

• "math.h" (implicitly via bcd.h & if compiled on PCC)

• <inttypes.h>

• <stdint.h>

• <stdio.h>

• <stdbool.h> (implicitly via bcd.h)

• <string.h> (implicitly via bcd.h)

• <stdlib.h> (implicitly via bcd.h & if not compiled on PCC)

• <math.h> (implicitly via bcd.h & if not compiled on PCC)

Solution

uint64_t p0016()

int main(int argc, char const *argv[])

Note

This function is only present in the Python test runner, or when compiling as a standalone program. It is not present when compiling for the Unity test runner.

/*
Project Euler Problem 16

This was fairly easy to do, given the BCD infrastructure I'd built up already, but I feel like there's a better way
to do it than this, if I could manage arbitrary-precision multiplication more efficiently.

Problem:

215 = 32768 and the sum of its digits is 3 + 2 + 7 + 6 + 8 = 26.

What is the sum of the digits of the number 21000?
*/
#ifndef EULER_P0016
#define EULER_P0016
#include <stdint.h>
#include <inttypes.h>
#include <stdio.h>
#include "include/macros.h"
#include "include/bcd.h"

uint64_t EMSCRIPTEN_KEEPALIVE p0016() {
    uint64_t answer = 0;
    BCD_int power = pow_cuint_cuint(256, 125);
    for (size_t i = 0; i < power.bcd_digits; i++)
        answer += (power.digits[i] & 0x0F) + (power.digits[i] >> 4);
    return answer;
}

PROGRAM_TAIL("%" PRIu64, p0016)
#endif

Tags: large-numbers, digit-sum, power