Trie(字典树)

#include<iostream>
int gcd(int a, int b) { return b ? gcd(b, a % b) : a; }
using namespace std;
typedef long long ll;
typedef pair<int, int> PII;
const int N = 100010, M = 3000000;
int son[M][2], idx, a[N];
void insert(int x){
    int p  =0;
    for(int i = 30;~i;--i){
        int &s = son[p][x >> i & 1];
        if(!s)s = ++idx;
        p = s;
    }
}
int query(int x){
    int p =0;
    int res = 0;
    for(int i = 30;~i;--i){
        int s = x >> i & 1;
        if(son[p][!s]){
            res += 1<<i;
            p = son[p][!s];
        }
        else p = son[p][s];
    }
    return res;
}
int main(){
    int n;cin >> n;
    for(int i  =0;i<n;++i){
        scanf("%d",&a[i]);
        insert(a[i]);
    }
    int ans =0;
    for(int i = 0;i<n;++i){
        ans = max(ans,query(a[i]));
    }
    printf("%d\n",ans);
    return 0;
}