Minimize Xor Difference

#include <bits/stdc++.h>

using namespace std;

#define _test   int _TEST; cin>>_TEST; while(_TEST--)

int main()
{
    _test
    {
        int a, b;
        cin>>a>>b;

        if(a == b)
        {
            cout<<0<<"\n";
            continue;
        }

        if(a<b)     swap(a, b);

        int bit = -1;

        for(int i=29; i>=0; i--)
        {
            int x = (1<<i);

            if((a&x) != (b&x))
            {
                bit = i;
                break;
            }
        }

        int ans = 0;

        for(int i=bit-1; i>=0; i--)
        {
            int x = (1<<i);

            if((a&x)>0 && (b&x)==0)
                ans += x;
        }

        cout<<ans<<"\n";
    }
}