Remove Duplicate Characters from a String

#include <stdio.h>

void removeDuplicates(char *str) {
    int visited[256] = {0};  // ASCII table

    int i = 0, j = 0;

    while (str[i] != '\0') {
        if (visited[(unsigned char)str[i]] == 0) {
            visited[(unsigned char)str[i]] = 1;
            str[j++] = str[i];  // keep character
        }
        i++;
    }

    str[j] = '\0';  // end string
}

int main() {
    char str[100];

    fgets(str, sizeof(str), stdin);

    // Remove newline if present
    int i = 0;
    while (str[i] != '\0') {
        if (str[i] == '\n') {
            str[i] = '\0';
            break;
        }
        i++;
    }

    removeDuplicates(str);

    printf("%s", str);

    return 0;
}