Convert String to Integer

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

int custom_atoi(const char *str) {
    // Your logic here
    char sign = str[0];
    int num = 0; 
    int diff = 1-'1';
    for(int i=0; str[i] != '\0'; i++){
        if(str[i] >= '0' && str[i] <= '9'){
            num = num*10 + str[i] + diff;
        }
        else{
            if(i>0){   
              break;
            }
        }
    }

    if(sign == '-'){
        num *= -1;
    }

    return 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;
}