The four adjacent digits in the 1000-digit number that have the greatest product are 9 × 9 × 8 × 9 = 5832.
73167176531330624919225119674426574742355349194934 96983520312774506326239578318016984801869478851843 85861560789112949495459501737958331952853208805511 12540698747158523863050715693290963295227443043557 66896648950445244523161731856403098711121722383113 62229893423380308135336276614282806444486645238749 30358907296290491560440772390713810515859307960866 70172427121883998797908792274921901699720888093776 65727333001053367881220235421809751254540594752243 52584907711670556013604839586446706324415722155397 53697817977846174064955149290862569321978468622482 83972241375657056057490261407972968652414535100474 82166370484403199890008895243450658541227588666881 16427171479924442928230863465674813919123162824586 17866458359124566529476545682848912883142607690042 24219022671055626321111109370544217506941658960408 07198403850962455444362981230987879927244284909188 84580156166097919133875499200524063689912560717606 05886116467109405077541002256983155200055935729725 71636269561882670428252483600823257530420752963450
Find the thirteen adjacent digits in the 1000-digit number that have the greatest product. What is the value of this product?
The answer is 23514624000, as surmised by the following program.
#include <iostream>
#include <vector>
#include <fstream>
int main(void)
{
std::string filePath = "./numbers.txt";
std::ifstream inFile;
unsigned long long largestProd = 0;
unsigned long long prodBuff;
std::vector<int> intVect;
char szBuff;
inFile.open(filePath.c_str());
// Load numbers into program
while(inFile.get(szBuff))
{
// Convert from ASCII value to integer literal
intVect.push_back(szBuff-48);
}
// Iterate through the vector, stopping 13 before intVect.end()
for(int i = 0; i < (intVect.size()-13); i++)
{
// Set prodBuff to the first of the 13 digits
prodBuff = intVect[i];
// Iterate through the list, multiplying against itself
for(int j = 1; j < 13; j++) { prodBuff *= intVect[i+j]; } // If is larger than current largest, replace if(prodBuff > largestProd)
{
largestProd = prodBuff;
}
}
// Output the answer
std::cout << largestProd;
}