# 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;
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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