C ++将while循环转换为do-while循环

Question

I see a ton a questions for converting for loops to while and do while loops, but I cant seem to find anything on converting while loops to do while loops in C++. It still needs to maintain the same function as the original code as well.

Here is the original code:

int number, product = 1, count = 0; 

cout << "Enter a whole number to be included in the product" 
<< endl << "or enter 0 to end the input: "; 
cin >> number; 

while (number != 0) 
{
product = product * number; 
count++; 
cout << "Enter a whole number to be included in the product" 
<< endl << "or enter 0 to end the input: "; 
cin >> number; 
} 

if (count > 0) 
{ 
cout << endl << "The product is " << product << "." << endl; 
} 

By moving it around, I was able to end up here, but I keep ending up with errors. When I run the program, it prompts me to enter a while number, like expected. If I enter a valid number, it loops and asks me the same question. Then when I enter 0, it kicks out as usual, but it displays that the product is 0 no matter the numbers entered before.

Here is my attempt at adjusting it into a do while loop:

int main()
{   

int number, product = 1, count = 0; 

do
{
    cout << "Enter a whole number to be included in the product" << endl << "or enter 0 to end the input: "; 
    cin >> number; 
    product = product * number; 
    count++; 
}

while (number != 0);
{
    if (count > 0) 
    cout << endl << "The product is " << product << "." << endl; 
}
}

Answer 1

In the do .. while loop when you insert 0, first you multiply product by 0, than it exists. Therefore the product is always 0.

Move the product before:

int count = -1, number = 1, product = 1; 
do
{
    count++;
    product = product * number; // you can use product *= number;
    cout << "Enter a whole number to be included in the product" << endl << "or enter 0 to end the input: "; 
    cin >> number;
}    
while (number != 0);

if (count > 0) 
    cout << endl << "The product is " << product << "." << endl;

Note: my code does not use additional if and still preserve the same functionality.

Answer 2

test number!=0 before assigning product = product*nuumber

otherwise, when user enters 0, you multiply by 0 and exit the loop

Answer 3

The problem is that in the do-while version, when the user inputs 0 this line:

product = product * number;

is executed, whereas in the while version not.

Because of this the product will always be 0.

If the number is 0 just don't multiply product .

Answer 4

Your problem was the number input on exit is 0, which makes your whole product equal to 0. Try this logic:

#include <iostream>

int main() {

    int number = 0, product = 1, count = 0;

    do {
        std::cout << "Enter a whole number to be included in the product" << std::endl << "or enter 0 to end the input: ";
        std::cin >> number;
        if (number > 0) {
            product = product * number;
            count++;
        }
    } while (number != 0);
    {
        if (count > 0)
            std::cout << std::endl << "The product is " << product << "." << std::endl;
    }
}

Answer 5

If you just want to solve the problem that you are getting a 0 as your answer, then the problem is due to the following lines

cin >> number; 
product = product * number; 

you take the number which is 0 and multiply it with the product and obviously the result will be 0.

you can fix it by putting a break statement.

cin >> number;
if(number == 0)
break;
product = product * number;

However, in general I am not sure what you are achieving by trying to solve this problem ie converting a while to a do-while.

Answer 6

int number, product = 1, count = 0; 

cout << "Enter a whole number to be included in the product" 
     << endl << "or enter 0 to end the input: "; 
cin >> number; // you enter a non-0 number here

while (number != 0) // you now loop until you hit 0 ...
{
    product = product * number; 
    count++; 
    cout << "Enter a whole number to be included in the product" 
         << endl << "or enter 0 to end the input: "; 
    cin >> number; // you overwrite the non-0 number you had previously input
} 

if (count > 0) 
{ 
    cout << endl << "The product is " << product << "." << endl; 
}

Without knowing the full context of your program, I'm guessing here, but you can probably rewrite it as:

int number = 0, product = 1, count = 0; 

do
{
    cout << "Enter a whole number to be included in the product" 
         << endl << "or enter 0 to end the input: ";
    cin >> number;
    if (number != 0)
    {
        count++;
        product *= number;
    } 
} while (number != 0); // exit the loop when you have a non-zero entry

if (count > 0) 
{ 
    cout << endl << "The product is " << product << "." << endl; 
}

Or ...

int number = 0, product = 1; 

do
{
    cout << "Enter a whole number to be included in the product" 
         << endl << "or enter 0 to end the input: ";
    cin >> number;
    if (number != 0)
    {
        product *= number;
    } 
} while (number != 0); // exit the loop when you have a non-zero entry

cout << endl << "The product is " << product << "." << endl; 

You can avoid the 2nd condition since you are excluding 0 from potential inputs, and simply always output a product.

Answer 7

You are increasing count regardless of the input you get. First check if the input was zero (your abort input).

Change

count++

to

if (number)
    count++;