Convert String to Integer

Code

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

int custom_atoi(const char *str) {
    int num = 0; 
    int neg = 0;
    if (*str == '-') { 
        neg = 1; 
        str++;
    } else if (*str == '+'){ 
        str++; 
    }
    while (*str != '\0'){ 
        if (*str >= '0' && *str <= '9') {
                // Build number from digits (ASCII to int)
                num = num * 10 + (*str - '0');
        } else { 
            if (neg){ 
                neg = -num; 
                return neg; 
            }
            return num;
        }
        str++; 
        } 
    if (neg){ 
        neg = -num; 
        return neg; 
    }
    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;
}

Solving Approach