C++ Implementation of Problem 34

View source code here on GitHub!

Includes

• "math.hpp"

• "macros.hpp" (implicitly, via math.hpp)

• <stdint.h>

• <iostream>

• <math.h> (implicitly, via math.hpp)

• <stdlib.h> (implicitly, via math.hpp)

• <stdint.h> (implicitly, via math.hpp)

• <inttypes.h> (implicitly, via math.hpp)

Solution

uint64_t p0034()

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.

/*
Project Euler Problem 34

Problem:

145 is a curious number, as 1! + 4! + 5! = 1 + 24 + 120 = 145.

Find the sum of all numbers which are equal to the sum of the factorial of
their digits.

Note: as 1! = 1 and 2! = 2 are not sums they are not included.
*/
#ifndef EULER_P0034
#define EULER_P0034
#include <stdint.h>
#include <iostream>
#include <cstdio>
#include "include/macros.hpp"
#include "include/math.hpp"

uint64_t EMSCRIPTEN_KEEPALIVE p0034() {
    uint64_t answer = 0, sum;
    for (uint64_t i = 10; i < 100000; i++) {
        sum = 0;
        char buf[8] = {};
        // I know snprintf exists, but it isn't defined in C++98,
        // and this isn't taking in user input
        sprintf(buf, "%" PRIu64, i);
        for (uint8_t j = 0; j < 8 && buf[j]; j++)
            sum += factorial(buf[j] - '0');
        if (sum == i)
            answer += i;
    }
    return answer;
}

PROGRAM_TAIL(p0034)
#endif

Tags: factorial, digit-sum