使用对象

import java.util.*;
import java.io.*;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);

        int n = Integer.parseInt(in.nextLine());
        String[] line = in.nextLine().split(" ");

        int ans = 0;
        Trie trie = new Trie();
        for (int i = 0; i < n; ++i) {
            int a = Integer.parseInt(line[i]);
            trie.insert(a);
            int b = trie.query(a);
            ans = Math.max(ans, a ^ b);
        }
        out.print(ans);
        out.flush();
    }

    static class Trie {
        Trie[] trie;
        int num;
        public Trie() {
            trie = new Trie[2];
        }

        public void insert(int x) {
            Trie root = this;
            for (int i = 30; i >= 0; --i) {
                int u = x >> i & 1;
                if (root.trie[u] == null) root.trie[u] = new Trie();
                root = root.trie[u];
            }
            root.num = x;
        }

        public int query(int x) {
            Trie root = this;
            for (int i = 30; i >= 0; --i) {
                int u = x >> i & 1;
                if (root.trie[u ^ 1] != null) root = root.trie[u ^ 1];
                else if (root.trie[u] != null) root = root.trie[u];
                else return root.num;
            }
            return root.num;
        }
    }
}

使用数组

import java.util.*;
import java.io.*;

public class Main {
    static int[][] son;
    static int idx;
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);

        son = new int[31 * 100010][2];
        int n = Integer.parseInt(in.nextLine());
        String[] line = in.nextLine().split(" ");

        int ans = 0;
        for (int i = 0; i < n; ++i) {
            int a = Integer.parseInt(line[i]);
            insert(a);
            int b = query(a);
            ans = Math.max(ans, a ^ b);
        }
        out.print(ans);
        out.flush();
    }

    private static void insert(int a) {
        int p = 0;
        for (int i = 30; i >= 0; i--) {
            int u = a >> i & 1;
            if (son[p][u] == 0) son[p][u] = ++idx;
            p = son[p][u];
        }
    }

    private static int query(int a) {
        int p = 0, res = 0;
        for (int i = 30; i >= 0; i--) {
            int u = a >> i & 1;
            if (son[p][u ^ 1] != 0) {
                res = res * 2 + u ^ 1;
                p = son[p][u ^ 1];
            } else {
                res = res * 2 + u;
                p = son[p][u];
            }
        }
        return res;
    }
}