How to Implement Your Own atoi() in C?
The equivalent of the atoi() function is easy to implement. One of the possible method to implement is shown below:
Approach
- Initialize res to 0.
- Iterate through each character of the string and update the res by multiplying it by 10 and keep adding the numeric value of the current digit. (res = res*10+(strg[i]-‘0’))
- Continue until the end of the string.
- return res.
Implementation of atoi() in C
C
// C program to Implement Custom atoi() #include <stdio.h> int atoi_Conversion(const char* strg) { // Initialize res to 0 int res = 0; int i = 0; // Iterate through the string strg and compute res while (strg[i] != '\0') { res = res * 10 + (strg[i] - '0'); i++; } return res; } int main() { const char strg[] = "12345"; int value = atoi_Conversion(strg); // print the Converted Value printf("String to be Converted: %s\n", strg); printf("Converted to Integer: %d\n", value); return 0; } |
Output
String to be Converted: 12345 Converted to Integer: 12345
To learn more about different approaches, refer to the article – Write your own atoi()
atoi() Function in C
In C, atoi stands for ASCII To Integer. The atoi() is a library function in C that converts the numbers in string form to their integer value. To put it simply, the atoi() function accepts a string (which represents an integer) as a parameter and yields an integer value in return.
C atoi() function is defined inside <stdlib.h> header file.
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