CSU 1216 异或最大值

Description

给定一些数，求这些数中两个数的异或值最大的那个值

Input

多组数据。第一行为数字个数n，1 <= n <= 10 ^ 5。接下来n行每行一个32位有符号非负整数。

Output

任意两数最大异或值

Sample Input

3
3
7
9

Sample Output

14

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <list>
#include <map>

using namespace std;

const int N = 100005 * 35;

int ans, n, arr[N], p;

struct Node
{
    Node *next[2];
} mem[N], *root;

Node *New()
{
    return &mem[p++];
}

void insert(int x)
{
    if (!root)
        root = New();
    Node *rt = root;
    for (int i = 31; i >= 0; i--)
    {
        int t = (x >> i) & 1;
        if (!rt->next[t])
            rt->next[t] = New();
        rt = rt->next[t];
    }
}

int ask(int x)
{
    Node *rt = root;
    int ret = 0;
    for (int i = 31; i >= 0; i--)
    {
        int t = (x >> i) & 1;
        if (rt->next[!t])
            ret |= 1 << i, rt = rt->next[!t];
        else
            rt = rt->next[t];
    }
    return ret;
}

int main()
{
    while (scanf("%d", &n) == 1)
    {
        ans = 0;
        p = 0;
        root = NULL;
        memset(mem, 0, sizeof(mem));
        for (int i = 1; i <= n; i++)
            scanf("%d", &arr[i]),
            insert(arr[i]);
        for (int i = 1; i <= n; i++)
            ans = max(ans, ask(arr[i]));
        printf("%d\n", ans);
    }
}