Convert a String to Float

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

float custom_atof(const char *str) {
    int i = 0;
    int sign = 1;
    float res = 0;
    int fpvalue = 0;
    if (str[i]=='-') {
        sign = -1;
        i = 1;
    }
    else if (str[i] == '+') {
        i = 1;
    }
    else i = 0;
    while (str[i]!='\0') {
        if (fpvalue != 0) {
            fpvalue++;
        }
        if (str[i]=='.') {
            fpvalue++;
            i++;
        }
        res = res * 10 + (str[i]-'0') * 1.00;
        i++;
    }
    while (fpvalue>0) {
        res/=10;
        fpvalue--;
    }

    return res*sign;
}

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;
}