Question

****I'm trying to compile this code, however, the answer still shows "0". This the formula I'm trying to use: (num1!) / ((num2!)(num1 - num2)! ) ***** (C++)

FOR INSTANCE; Big Number = 20 and Small Number = 3

#include <iostream>

using namespace std;

int factorial(int num1, int num2){

unsigned long long answer = 0;
unsigned long long top = 1;
unsigned long long bottom = 1;
unsigned long long bottom2 = 1;
unsigned long long bottom_3 = 1;
int num3 = num1 - num2;

for(int i = 1 ; i <=num1; i++){
top *= i;
}
cout << "Top: " << top << endl;

for(int i = 1 ; i <=num3; i++){
bottom *= num3;
}
cout << "Bottom: " << bottom << endl;;
for(int i = 1 ; i <=num2; i++){
bottom2 *= num2;
}
cout << "Bottom 2: " << bottom2 << endl;;

bottom_3 = bottom2 * bottom;
cout << "Bottom3 : " << bottom_3 << endl;
answer = (top / bottom_3);

cout << "Answer@FACTORIAL: " << answer << endl;

return answer;
}

int main() {
int num1 = 0;
int num2 = 0;
unsigned long long answer = 0;

cout << "Insert BIG number" << endl;
cin >> num1;

cout<< "Insert SMALL number" << endl;
cin >> num2;

answer = factorial(num1, num2);

cout << "Answer: "<<answer << endl;;
}

Answer 1

//modified a logic mistake

#include <iostream>

using namespace std;

int factorial(int num1, int num2){

unsigned long long answer = 0;
unsigned long long top = 1;
unsigned long long bottom = 1;
unsigned long long bottom2 = 1;
unsigned long long bottom_3 = 1;
int num3 = num1 - num2;

for(int i = 1 ; i <=num1; i++){
top *= i;
}
cout << "Top: " << top << endl;

for(int i = 1 ; i <=num3; i++){
bottom *= i;//modified here
}
cout << "Bottom: " << bottom << endl;;
for(int i = 1 ; i <=num2; i++){
bottom2 *= i;//modified here
}
cout << "Bottom 2: " << bottom2 << endl;;

bottom_3 = bottom2 * bottom;
cout << "Bottom3 : " << bottom_3 << endl;
answer = (top / bottom_3);

cout << "Answer@FACTORIAL: " << answer << endl;

return answer;
}

int main() {
int num1 = 0;
int num2 = 0;
unsigned long long answer = 0;

cout << "Insert BIG number" << endl;
cin >> num1;

cout<< "Insert SMALL number" << endl;
cin >> num2;

answer = factorial(num1, num2);

cout << "Answer: "<<answer << endl;;
}

output:

Insert BIG number
20
Insert SMALL number
3
Top: 2432902008176640000
Bottom: 355687428096000
Bottom 2: 6
Bottom3 : 2134124568576000
Answer@FACTORIAL: 1140
Answer: 1140

Process exited normally.
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