Convert String to Integer

Code

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

int custom_atoi(const char *str) {
    int positive = 1;
    int index = 0;
    if (str[index] == '-') {
        positive = 0;
        index++;
    } else if (str[index] == '+') {
        index++;
    }

    int val = 0;
    while (str[index]) {
        int digit = str[index] - '0';
        if (0 <= digit && digit <= 9) {
            val *= 10;
            val += digit;
        } else {
            break;
        }
        index++;

    }
    return (positive)? val: -val;
}

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