Convert a String to Float

Code

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

#define NUM_ZERO ('0')
#define NUM_NINE ('9')
#define SIGN_MINUS ('-')
#define SIGN_PLUS ('+')
#define DOT ('.')

#define IS_NUMERIC(chr) ((chr) >= NUM_ZERO && (chr) <= NUM_NINE)
#define IS_SIGN_MINUS(chr) ((chr) == SIGN_MINUS)
#define IS_SIGN_PLUS(chr) ((chr) == SIGN_PLUS)
#define IS_DOT(chr) ((chr) == DOT)
#define CHAR2NUM(chr) ((chr) - NUM_ZERO)

float custom_atof(const char *str) {
    // Your logic here
    float sign = 1.0f;
    float num_int = 0.0f;
    float num_fract = 0.0f;
    float num_divisor = 1.0f;
    if(IS_SIGN_MINUS(*str)){
        sign = -1.0f;
        str++;
    }
    else if(IS_SIGN_PLUS(*str)){
        sign = 1.0f;
        str++;
    }
    while((*str) && IS_NUMERIC(*str))
    {
        num_int = num_int*10.0f + CHAR2NUM(*str);
        str++;
    }
    if(IS_DOT(*str))
    {
        str++;
        while((*str) && IS_NUMERIC(*str))
        {
            num_fract = num_fract*10.0f + CHAR2NUM(*str);
            num_divisor *= 10.0f;
            str++;
        }
    }

    return sign*(num_int+num_fract/num_divisor);
}

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++;
    }

    float value = custom_atof(str);
    printf("%.2f", value);
    return 0;
}

Solving Approach