Largest Product in Series _More efficient than First one
/*
Problem statement--
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?
*/
#include <stdio.h>
#include <inttypes.h>
#include <string.h>
int main()
{
// Just put the value of numbers to multiply in 'count' variable
int count = 4;
char array[] = "731671765313306249192251196744265747423553491949
3496983520312774506326239578318016984801869478851843858615607891
1294949545950173795833195285320880551112540698747158523863050715
6932909632952274430435576689664895044524452316173185640309871112
1722383113622298934233803081353362766142828064444866452387493035
8907296290491560440772390713810515859307960866701724271218839987
9790879227492190169972088809377665727333001053367881220235421809
7512545405947522435258490771167055601360483958644670632441572215
5397536978179778461740649551492908625693219784686224828397224137
5657056057490261407972968652414535100474821663704844031998900088
9524345065854122758866688116427171479924442928230863465674813919
1231628245861786645835912456652947654568284891288314260769004224
2190226710556263211111093705442175069416589604080719840385096245
5444362981230987879927244284909188845801561660979191338754992005
2406368991256071760605886116467109405077541002256983155200055935
72972571636269561882670428252483600823257530420752963450";
int last = (sizeof(array) / sizeof(char));
uint64_t max_product = 1;
uint64_t product = 1;
// first ""count"" digits product
for (int i = 0; i < count; i++)
{
max_product = max_product * (array[i] - '0');
}
for (int x = count; x < (last); x++)
{
if ((array[x - count] - '0') != 0) // check if division is performed by zero
{
product = ((product / (array[x - count] - '0')) * (array[x] - '0'));
}
else // to avoid division by zero error
{
product = array[(x - count) + 1] - '0';
for (int j = ((x - count) + 2); j < (x + 1); j++)
{
product = product * (array[j] - '0');
}
}
// if product is larger then store product in maximum_product.
if (product > max_product)
{
max_product = product;
printf("\nMax prod : %" PRIu64 "\n", max_product);
}
}
printf("\nMax prod : %" PRIu64 "\n", max_product);
return 0;
}