Convert String to Integer

Code

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

int custom_atoi(const char *str) {
    int i = 0;
    int sign = 1;
    int value = 0;

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

    // Parse digits until non-digit or end of string
    while (str[i] != '\0') {
        if (str[i] >= '0' && str[i] <= '9') {
            value = value * 10 + (str[i] - '0');
        } else {
            break;  // stop at first non-digit
        }
        i++;
    }

    return sign * value;
}

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