Find last k digits in product of an array numbers in C++

Suppose we have an array of n elements called A. We have another number k. Our task is to find last k digits of the product of elements in the array A. Suppose the A = [15, 22, 13, 19, 17], then the product is 1385670, the last k = 3 digits are 670.

To solve this problem, we will multiply the numbers under modulo 10^k.

Example

 Live Demo

#include<iostream> #include<cmath> using namespace std; int displayLastKNumbers(int array[], int n, int k) {    int mod = (int)pow(10, k);    int mul = array[0] % mod;    for (int i = 1; i < n; i++) {       array[i] = array[i] % mod;       mul = (array[i] * mul) % mod;    }    return mul; } int main() {    int a[] = {15, 22, 13, 19, 17};    int k = 3;    int n = sizeof(a) / sizeof(a[0]);    cout <<"Last K digits are: " << displayLastKNumbers(a, n, k); }

Output

Last K digits are: 670