Convert String to Integer

Code

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

int custom_atoi(const char *str) {
    char *p = (char *)str;
    int data = 0;
    int polarity = 1;
    do {
        if (*p >= '0' && *p <= '9') {
            data *= 10;
            data += *p - '0';
        } else if (*p == '-') {
            polarity = -1;
        } else if (*p == '+') {
            polarity = 1;
        } else {
            break;
        }
    } while (*p++);
    return (polarity * data);
}

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