Convert String to Integer

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

int custom_atoi(const char *str) {
    // Your logic here
    if (!str) return 0;
    int i = 0;
    int num = 0;        //res
    int sign = 1;       //flag

    //skip 'space' 
    while (str[i] == ' ' || str[i] == '\n' || str[i] == '\t') { 
        i++;
    }

    //alter flag sign
    if (str[i] == '+') {            
        i++;
    } else if (str[i] == '-') {
        sign = -1;
        i++;
    }

    //snowball
    while (1) {
        char c = str[i];

        if (c >= '0' && c <= '9') {
            num = num * 10 + (c - '0');
        } else {
            break;
        }
        i++;
    }
    return num * 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++;
    }

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