Remove Duplicate Characters from a String

Code

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

void remove_duplicates(char *str) {
    size_t len = strlen(str);
    for (int i = 0; i < len; i++)
    {
        for (int j = i + 1; j < len; j++)
            if (str[i] == str[j])
                str[j] = 0;
    }

    int last_zero_index = 0;
    for (int i = 0; i < len; i++)
    {
        while (str[last_zero_index] != 0)
            last_zero_index++;
        if (str[i] && i > last_zero_index)
        {
            str[last_zero_index] = str[i];
            str[i] = 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;
}

Solving Approach