暴力+构造
If r - l ≤ 4 we can all subsets of size not greater than k. Else, if k = 1, obviously that answer is l. If k = 2, answer is 1, because xor of numbers 2x and 2x + 1 equls 1. If k ≥ 4 answer is 0 because xor of to pairs with xor 1 is 0.
If k = 3, we can choose numbers 2x and 2x + 1 with xor 1. So we need to know, if we can get xor equals 0. Suppose that there are 3 such numbers x, y and z (r ≥ x > y > z ≥ l) with xor equals 0. Consider the most non-zero bit of numberx. At the same bit of y it's also 1, because xor equls 0, and y > z. Consider the next bit of numbers. If z have 0 there, we have to do next: set the previous bit of numbers x and y equals 0, and set current bit equals 1. Obviously xor still equals 0, z hadn't changed and numbers x and y stood closer to z, so they are still at [l, r].And x > y.Consider the next bit of numbers. If z has zero here than we will change most bits of x и y at the same way and so on. z > 0, so somewhen we will get to bit in which z has 1. Since xorequals 0, the same bit of x would be 1 because x > y, and y would have 0 there. At the next bits we will change bit in x to 0, and in numbers y and z to 1.Finally z would be greater or equal than before, and x would be less or greater than before, and x > y > z would be correct. So, we have the next: if such numbers x, y and z exist than also exist numbers:
1100…000
1011…111
0111…111
with xor equals 0. There are not much such triples, so we can check them.
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
typedef long long int LL;
LL L,R,K;
LL ans=0x3f3f3f3f3f3f3f3f;
int main()
{
cin>>L>>R>>K;
if(R-L+1<=4)
{
LL m=R-L+1;
LL sig=0;
for(LL i=1;i<(1LL<<m);i++)
{
LL temp=0;
LL wei=0;
LL si=i;
while(si)
{
wei++;
si=si&(si-1);
}
if(wei>K) continue;
for(LL j=0;j<m;j++)
{
if(i&(1LL<<j))
{
temp^=L+j;
}
}
if(temp<ans)
{
ans=temp;
sig=i;
}
}
cout<<ans<<endl;
LL wei=0;
LL tsig=sig;
while(tsig)
{
wei++;
tsig=tsig&(tsig-1);
}
cout<<wei<<endl;
for(LL i=0;i<m;i++)
{
if(sig&(1<<i))
{
cout<<L+i<<" ";
}
}
cout<<endl;
}
else
{
if(K==1)
{
cout<<L<<endl;
cout<<1<<endl;
cout<<L<<endl;
}
else if(K==2)
{
if(L%2) L++;
cout<<1<<endl;
cout<<2<<endl;
cout<<L<<" "<<L+1<<endl;
}
else if(K==3)
{
bool flag=false;
LL mx=3,mi=1;
while(mx<=R)
{
if(mi>=L)
{
flag=true;
cout<<0<<endl<<3<<endl;
cout<<mx<<" "<<mx-1<<" "<<mi<<endl;
break;
}
mx<<=1LL;
mi<<=1LL; mi++;
}
if(flag==false)
{
if(L%2) L++;
cout<<1<<endl;
cout<<2<<endl;
cout<<L<<" "<<L+1<<endl;
}
}
else
{
cout<<0<<endl;
cout<<4<<endl;
if(L%2) L++;
cout<<L<<" "<<L+1<<" "<<L+2<<" "<<L+3<<endl;
}
}
return 0;
}