CODEWITHSUNDEEP
cloopsfactorial
Chroma
Chroma

Reputation: 23

Factorial program in c

Trying to make a code that gets the factorial of the inputted number.

int factorial(int number, int i)
{
    int endval;
    for(i = number - 1; i>0; i--){
        endval = number * i;
    }
    if (endval == 0){
        printf("1");
    }
    return endval;
}

int main()
{
    int endvalue, numA, numB;
    char userchoice[1];
    printf("Enter a choice to make (f for factorial): \n");
    scanf("%s", userchoice);
    if(strcmp(userchoice, "f")== 0){
        printf("Enter a value to get it's factorial: ");
        scanf("%d", &numA);
        endvalue = factorial(numA, numB);
        printf("%d", endvalue);
        return 0;}


    getch();
    return 0;
}

For some reason the whole for loop doesn't do anything in the function when I set the answer (number*i)= endval. It just prints out the same number I inputted and gives me an absurd answer for 0!.

int factorial(int number, int i)
{
    int endval;
    for(i = number - 1; i>0; i--){
            endval = number * i;
    }
    if (endval == 0){
        printf("1");
    }
    return endval;
}

However the code works perfectly fine when I remove endval variable entirely (with the exception that it gets 0! = 10)

int factorial(int number, int i)
{
    for(i = number - 1; i>0; i--){
        number = number * i;
    }
    if (number == 0) {printf("1");}
    return number;
}

Is there anything I missed in the code that's causing these errors?

Upvotes: 0

Views: 280

Answers (3)

miroslav licko
miroslav licko

Reputation: 81

There are possibly few things to correct. See please attached code.

int factorial(int number)
{

    if (number == 0){ return 1; }

    int endval=1, i;

    for(i = 1; i<=number; i++) { endval *= i; }

    return endval;

}

int main() {

    int endvalue, numA;
    char userchoice[1];
    printf("Enter a choice to make (f for factorial): \n");
    scanf("%s", userchoice);

    if(strcmp(userchoice, "f")== 0) {

        printf("Enter a value to get it's factorial: ");
        scanf("%d", &numA);
        endvalue = factorial(numA);
        printf("%d", endvalue);
        return 0;

    }

getch();
return 0;
}

Upvotes: 0

Jaguar Nation
Jaguar Nation

Reputation: 132

A definiton of factorial is:
factorial(0) = 1
factorial(n) = n * factorial(n-1)
Note: Factorial is legal only for number >= 0

In C, this definition is:

 int factorial(int number)
    {
         if (number < 0)
             return -1;

         if (number == 0)
              return (1);
    
         /*else*/
         return (number * factorial(number-1));
    }

Upvotes: 1

EsmaeelE
EsmaeelE

Reputation: 2708

#include <stdio.h>
#include <string.h>

int factorial(int number)
{
    int endval=1;
    for(int i = number ; i>0; i--){
        endval *= i;
    }
    return endval;
}

int main()
{

    int endvalue=0;
    int numA=0;

    char userchoice[1];
    printf("Enter a choice to make (f for factorial): ");
    int ret=scanf("%s", userchoice);
    if (!ret){
        printf("Error in scanf: %d", ret);
    }
    if(strcmp(userchoice, "f")== 0){
        printf("Enter a value to get it's factorial: ");
        scanf("%d", &numA);
        endvalue = factorial(numA);
        printf("%d", endvalue);
        return 0;
    }

    getchar();
    return 0;
}

Code with some changes will work

  • factorial() function can get only one argument.
  • As a good habit all variables must be initialized.
  • Add include statement to source and be explicit not rely on compiler. As we use strcmp() we must include string.h
  • use standard getchar() instead of getch()
  • Also can check return value of library function scanf() to ensure reading is correct or not.
  • You can use warnings from compiler to get most of above notes. In gcc: gcc -Wall code.c
  • Use a debugger to run program line by line and monitor variables value in each steps or use as many printf() to see what happens in function call.

Upvotes: 0

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