Remove Duplicate Characters from a String

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

void remove_duplicates(char *str) {
    if (str == NULL) return;

    int seen[256] = {0}; 
    int write = 0;      

    for (int read = 0; str[read] != '\0'; read++) {
        unsigned char current = str[read];
        if (seen[current] == 0) {
            seen[current] = 1;       
            str[write] = str[read];    
            write++;                   
        }
    }
    str[write] = '\0';
}

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++;
    }

    remove_duplicates(str);
    printf("%s", str);
    return 0;
}