Trie (binary)

/*
tutorial : https://threads-iiith.quora.com/Tutorial-on-Trie-and-example-problems
problem : http://codeforces.com/contest/842/problem/D
*/
#include<bits/stdc++.h>
using namespace std;

#define si(n) scanf("%d",&n)


struct Trie{
    Trie * nxt0;
    Trie * nxt1;
    int sz;
    Trie() : nxt0(NULL),nxt1(NULL),sz(0){}
};

typedef Trie * trie;

const int MAX = 3e5+5;
const int MAXLOG =20;

int used[MAX];

void add(trie root,int n)
{
    root->sz ++;
    for(int i=MAXLOG-1;i>=0;i--){
        if(n & (1<<i)){
            if(root->nxt1 ==NULL)
                root->nxt1=new Trie();
            root=root->nxt1;
        }
        else{
            if(root->nxt0==NULL)
                root->nxt0=new Trie();
            root=root->nxt0;
        }
        root->sz++;
    }

}

int safe_sz(trie a){
    if(!a)return 0;
    return a->sz;
}

int mex(trie root)
{
    int ans=0;
    for(int i=MAXLOG-1;i>=0;i--){
        if(root==NULL)return ans;
        if(root->nxt0==NULL && root->nxt1==NULL)
            return ans;
        if(used[i]%2==0){
            if(safe_sz(root->nxt0) != (1<<i))
                root=root->nxt0;
            else{
                ans+=(1<<i);
                root=root->nxt1;
            }
        }
        else{

            if (safe_sz(root -> nxt1) != (1 << i)) {
                root = root -> nxt1;
            }
            else {
                ans += (1 << i);
                root = root -> nxt0;
            }
        }
    }
    return ans;
}

int main()
{
    int n,m,i,j,p;
    si(n);si(m);
    trie root=new Trie();
    map<int,int>gg;
    while(n--){
        si(p);
        if(++gg[p]==1){
            add(root,p);
        }
    }

    for(i=0;i<m;i++){
        si(p);
        for(j=MAXLOG-1;j>=0;j--){
            if(p & (1<<j))
                used[j]++;
        }
        printf("%d\n",mex(root));
    }
    return 0;
}