CODEWITHSUNDEEP
cloopsif-statementchar
Ishan Ahmed
Ishan Ahmed

Reputation: 105

how can i break a loop by checking a condition

I am trying to sum some integers and when I press '=' the loop will terminate and print the sum of those values. I am trying to give a space before press equal.

#include <stdio.h>

int main()
{
    int a, sum = 0;
    char b;

    while (1) {
        scanf("%d", &a);
        scanf(" %c", &b);

        sum += a;

        if(b == '=')
            break;
    }

    printf("sum = %d", sum);

    return 0;
}

Upvotes: 0

Views: 98

Answers (2)

4386427
4386427

Reputation: 44274

The two scanf, i.e.

    scanf("%d", &a);
    scanf(" %c", &b);

will work like this:

Input: "1 2 3 4 ="

In the first loop a will become 1 and b will become 2.

In the second loop a will become 3 and b will become 4.

Now the remaining string is " ="

So in the third loop there is no integer to scan and consequently a will still have the value 3. b will get the value = and the loop terminates.

So sum is 1 + 3 + 3, i.e. 7

You can check that using simple printf statements:

    scanf("%d",&a);
    printf("a=%d\n",a);
    scanf(" %c",&b);
    printf("b=%c\n",b);

Input:
1 2 3 4 =

Output:
a=1
b=2
a=3
b=4
a=3
b==
sum= 7

Remember: Always check the value returned by scanf - like:

if (scanf("%d",&a) != 1)
{
    // Error - didn't scan an integer
    // add error handling
    ...
}

So you can do

while(1){
    if (scanf("%d",&a) != 1)
    {
        // No integer found
        
        // Add error handling...
        // For now - just stop the loop
        break;
    }
    sum+=a;
}

For input like "1 2 3 4 =" this give the result 10.

However, input like "1 2 3 4 HelloWorld" will also give the result 10, i.e. any non-integer input simply terminates the loop. If you only want the loop to terminate when the input is =, you can extend the error-handling.

Upvotes: 2

lnogueir
lnogueir

Reputation: 2085

Your issue is because you are doing scanf twice in your loop.

Do this instead:

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

int main()
{
    int sum=0;
    char a[10];
    while(1){
        scanf("%9s", a); // makes sure we won't have memory overflow 
        if(strcmp(a, "=") == 0)
            break;
        sum+=atoi(a);
    }
    printf("sum= %d",sum);

    return 0;
}

Upvotes: 1

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