The Hamming Distance Problem

#include<bits/stdc++.h>

using namespace std;

char str[20];

int main()
{
    int test,i,n,h;

    scanf("%d",&test);

    while(test--)
    {
        scanf("%d%d",&n,&h);

        for(i=0;i<n-h;i++)
        {
            str[i] = '0';
        }

        for(i=n-h;i<n;i++)
        {
            str[i] = '1';
        }

        str[n] = '\0';

        printf("%s\n",str);

        while(next_permutation(str,str+n))
        {
            printf("%s\n",str);
        }

        if(test)
        {
            puts("");
        }
    }

    return 0;
}