B题求异或最小值,即同或最大值(过了94,哭了)Help

#include<iostream>

#include<map>

#include<algorithm>

using namespace std;

unsigned int a[200020],ni=0x3f3f3f3f;

unsigned int n,m,pan=0;

map<unsigned int,unsigned int> mp;

int main()

{

cin>>n>>m;

for(long long i=1;i<=n;i++)

{

cin>>a[i];

mp[a[i]]++;

if(mp[a[i]]>=2){pan=1;}

}

sort(a+1,a+1+n);

if(pan)cout<<(1<<m)-1<<endl;

else{

for(long long i=1;i<n;i++)

{

ni=min(ni,a[i]^a[i+1]);

}

cout<<(1<<m)-1-ni<<endl;

}

}