Convert String to Integer

Code

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

int custom_atoi(const char *str) {
    uint8_t idx = 0;
    int res = 0;
    bool neg = false;

    if ('-' == str[idx]) {
        neg = true;
    }else if ('+' == str[idx]) {
        neg = false;
    }else if (str[idx] >= '0' && str[idx] <= '9'){
        res = (str[idx] - '0');
    } else {
        return res;
    }

    idx++;
    
    while (str[idx] != '\0') {
        if (str[idx] >= '0' && str[idx] <= '9') {
            if (true == neg) {
                res = res * 10 - (str[idx] - '0');
            } else {
                res = res * 10 + (str[idx] - '0');
            }
            
        } else {
            break;
        }

        idx++;
    }

    return 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++;
    }

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

Solving Approach