最大异或对

最大异或对

#include <bits/stdc++.h>
using namespace std;

const int N = 1e5 + 10, M = 31 * N;

int n;
int a[N];
int son[M][2], idx;
void insert(int x){
    int p = 0;
    for(int i = 30; i >= 0; --i){
        int u = x >> i & 1;
        if(!son[p][u]) son[p][u] = ++idx;
        p = son[p][u];
    }
}
int query(int x){
    int p = 0;
    int res = 0;
    for(int i = 30; i >= 0; --i){
        int u = x >> i & 1;
        if(son[p][!u]){
            p = son[p][!u];
            res = res * 2 + !u;
        }else{
            p = son[p][u];
            res = res * 2 + u;
        }
    }
    return res;
}
signed main(){
    scanf("%d", &n);
    for(int i = 0; i < n; ++i) scanf("%d", &a[i]);
    
    int res = 0;
    for(int i = 0; i < n; ++i){
        insert(a[i]);
        int t = query(a[i]);
        res = max(res, t ^ a[i]);
    }
    
    printf("%d\n", res);
    
    return 0;
}