就直接贴代码了。ps: Trie里的next用vector的话会MLE，所以就改成了数组

#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
typedef long long ll;
ll nums[100010];
class Trie{
public:
    Trie* next[2];
    bool isNum;
    Trie() {
        next[0] = 0;
        next[1] = 0;
        isNum = false;
    }
    ~Trie() {
        del(this);
    }
    void add(ll num) {
        Trie* curr = this;
        for(int i = 31; i >= 0; i --) {
            int bit = (num >> i) & 1;
            if(!curr->next[bit]) {
                curr->next[bit] = new Trie();
            }
            curr = curr->next[bit];
        }
        curr->isNum = true;
    }
    ll search_max(ll num) {
       ll res = 0;
       Trie* curr = this;
       int target;
       for(int i = 31; i >= 0; i --) {
           res <<= 1;
           int bit = (num >> i) & 1;
           int rebit = 1-bit;
           target = bit;
           if(curr->isNum == true) return res;
           if(curr->next[rebit]) {
               res += 1;
               target = rebit;
           }
           if(curr->isNum == false) curr = curr->next[target];
       }
       return res;
    }
private:
    void del(Trie* curr) {
        for(auto ptr: curr->next) {
            del(ptr);
        }
        delete curr;
    }
};

int main() {
    int n;
    cin >> n;
    ll res = 0;

    Trie* t = new Trie();

    for(int i = 1; i <= n; i ++) {
        cin >> nums[i];
        t->add(nums[i]);
    }

    for(int i = 1; i <= n; i ++) {
        res = max(res, t->search_max(nums[i]));
    }
    cout << res << endl;
    return 0;
}