子数组的最大异或和

链接
数组异或和的定义：把数组中所有的数异或起来得到的值。给定一个整型数组arr，其中可能有正、有负，有零，求其中子数组的最大异或和

从高位向低位选择

import java.util.Scanner;

public class Main {

    private static int solve(int[] data) {
        if (data == null || data.length == 0) {
            return 0;
        }

        Trie trie = new Trie();
        trie.add(0);
        int sum = 0;
        int ret = data[0];
        for (int i = 0; i < data.length; ++i) {
            sum ^= data[i];
            ret = Math.max(ret, trie.query(sum));
            trie.add(sum);
        }

        return ret;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while (in.hasNext()) {
            int n = in.nextInt();
            int[] arr = new int[n];
            for (int i = 0; i < n; ++i) {
                arr[i] = in.nextInt();
            }
            System.out.println(solve(arr));
        }
    }
}

class Trie {

    private Node root;

    class Node {
        Node[] children = new Node[2];
    }

    public Trie() {
        this.root = new Node();
    }

    public void add(int n) {
        Node cur = this.root;
        for (int i = 31; i >= 0; --i) {
            int digit = (n >> i) & 1;
            if (cur.children[digit] == null) {
                cur.children[digit] = new Node();
            }
            cur = cur.children[digit];
        }
    }

    public int query(int n) {
        Node cur = this.root;
        int ret = 0;
        for (int i = 31; i >= 0; --i) {
            int digit = (n >> i) & 1;
            int best = i == 31 ? digit : digit ^ 1;
            if (cur.children[best] == null) {
                best ^= 1;
            }
            ret |= ((best ^ digit) << i);
            cur = cur.children[best];
        }
        return ret;
    }
}