C Language: Custom atoi() function

Last update on December 20 2024 13:02:41 (UTC/GMT +8 hours)

C - Implementing a custom atoi() function.

The atoi() function is used to convert a character string to an integer value.

Code:

# include <stdio.h>

int my_atoi(const char *str) {
    int result = 0;
    int sign = 1;
    int i = 0;

    // Check for leading sign character
    if (str[0] == '-') {
        sign = -1;
        i++;
    }
    else if (str[0] == '+') {
        i++;
    }

    // Convert digits to integer value
    while (str[i] != '\0') {
        if (str[i] < '0' || str[i] > '9') {
            break;
        }
        result = result * 10 + (str[i] - '0');
        i++;
    }

    return sign * result;
}

int main() {
    const char *str1 = "-1234";
    int result = my_atoi(str1);
    printf("Converted integer: %d\n", result);
    const char *str2 = "1234";
    result = my_atoi(str2);
    printf("\nConverted integer: %d\n", result);
    return 0;
}

Output:

Converted integer: -1234

Converted integer: 1234

The my_atoi() function takes a string as input and returns the corresponding integer value. It checks for a leading sign character and converts the remaining digits to an integer value.