prob8.cpp

#include <iostream>
#include <cmath>
#include <cstdlib>
#include <vector>
#include <cstdint>
#include <cassert>

#define WIDTH 5
#define BIGNUM "7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450"

int main(int argc, char *argv[])
{               
    // convert input string of numbers into array of ints
    std::string input = BIGNUM;
    int length = input.length();
    assert(length >= 5);
    int* int_array = new int[length];
    for (int j = 0; j < length; j++)
        int_array[j] = (int)input[j] - 48;

    // find largest product of five consecutive ints in array
    int largest = 0;
    for (int k = 4; k <= length; k++)
    {
        int prod = 1;
        for (int j = 0; j < WIDTH; j++)
            prod *= int_array[k - j];
        if (prod > largest)
            largest = prod;
    }
    
    std::cout << largest << std::endl;
    return 0;
}