#include <bitset>
#include <cstring>

void removeDuplicate( char *s ) {
    if( s == NULL ) return;
    int n = std::strlen(s);
    if( n < 2 ) return;

    std::bitset<256> exist;
    exist.reset();
    exist.set(s[0]);

    int tail=1;
    for( int i=1; i<n; ++i )
        if( !exist.test(s[i]) ) {
            s[tail++] = s[i];
            exist.set(s[i]);
        }

    for( int i=tail; i<n; ++i )
        s[i] = 0;
}