Convert String to Integer

Code

#include <stdio.h>
#include <stdint.h>

#define NUM_ZERO ('0')
#define NUM_NINE ('9')
#define SIGN_MINUS ('-')
#define SIGN_PLUS ('+')
#define IS_NUMERIC(chr) (((chr>=NUM_ZERO) && (chr<=NUM_NINE))?1:0)
#define IS_SIGN_MINUS(chr) ((chr==SIGN_MINUS)?1:0)
#define IS_SIGN_PLUS(chr) ((chr==SIGN_PLUS)?1:0)
#define CHAR2NUM(chr) (chr - NUM_ZERO)
int custom_atoi(const char *str) {
    // Your logic here
    int num = 0;
    int sign = 1;
    if(IS_SIGN_MINUS(*str))
    {
        sign = -1;
        str++;
    }
    else if(IS_SIGN_PLUS(*str))
    {
        sign = 1;
        str++;
    }
    while (*str && IS_NUMERIC(*str)) {
        num = num * 10 + CHAR2NUM(*str);
        str++;
    }
    return sign*num;
}

int main() {
    char str[101];
    fgets(str, sizeof(str), stdin);

    // Remove newline
    uint8_t i = 0;
    while (str[i]) {
        if (str[i] == '\n') {
            str[i] = '\0';
            break;
        }
        i++;
    }

    printf("%d", custom_atoi(str));
    return 0;
}

Solving Approach