C Program to Convert String to Integer Without Using Library Function atoi()

Problem:- How to convert a string to integer without using library functions in c or Convert String to Integer without library function in C or C program to convert string to integer without using atoi function or How to Convert String to Integer without using any BuiltIn Functions ? or C Program to Convert String to Integer or How to convert string to integer in C or C Program to Convert String to Integer or How to convert INTEGER to STRING without using library functions or C Program which Converts an Integer to String & vice-versa or C Program to Convert String to Integer Without Using Library Function atoi()

Explanation:- here we are converting a string to integer without using an atoi library function, first pass the string to a function and then compare with the first if else condition if condition is true then we can not convert a string into integer and if the condition is false then we can convert a string to integer number. Here we took an input number as a string, not as an integer that is why we have to convert the number to an integer or if we input the string then we cannot convert it.

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Solution:-

#include<stdio.h>

#include<string.h>

int strToint (char[]);

int main()

{

/*Visit - www.programmingwithbasics.com*/

   

    printf("=====================================");

    printf("\nVisit - www.programmingwithbasics.com");

    printf("\n=====================================");

    

    while(1)

    {

    char str[10];

    int intNum;

    printf("\n\nEnter Integer Number: ");

    scanf("%s",str);

    intNum = strToint(str);

if(intNum==0)

{

printf("\nEnter The Number Not String\n\n");

}

else

    {

    printf("\n\nEquivalent Integer Value: %d",intNum);

}

}

return 0;

}

int strToint (char str[])

{

    int i=0,sum=0;

    while(str[i] != '\0')

  {

        if(str[i] < 48 || str[i] > 57)

  {

            printf("\n\nCan't Convert Into Integer");

            return 0;

        }

        else

  {

            sum = sum*10 + (str[i] - 48);

            i++;

        }

    }

return sum;

}

return sum;

}

Output:-

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