Convert a String to Float

Code

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

float custom_atof(const char *str) {
    
    float res = 0.0f;
    int idx = 1;
    int frac_ctr = 0;
    int sign = 1;


    if (*str == '-') {
        sign = -1;
    } else if (*str == '+') {
        sign = 1;
    } else if (*str >= '0' && *str <= '9') {
        res += (*str - '0');
    } else {
        return res;
    }

    while (str[idx] != '\0') {
        frac_ctr *= 10;
        if ('.' == str[idx]) {
            frac_ctr = 1.0f;
        }else if (str[idx] >= '0' && str[idx] <= '9') {
            res = res * 10 + str[idx] - '0';
        }
        
        idx++;
        
    }

    if (frac_ctr != 0) {
        res /= frac_ctr;
    }
    
    return sign * res;
}

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