Trie URAL 7192 Chip Factory (15长春J)

/************************************************
* Author        :Running_Time
* Created Time  :2015/11/1 14:58:49
* File Name     :J.cpp
************************************************/

#include <cstdio>
#include <algorithm>
#include <iostream>
#include <cstring>
#include <cmath>
#include <string>
#include <vector>
#include <queue>
#include <deque>
#include <stack>
#include <list>
#include <map>
#include <set>
#include <bitset>
#include <cstdlib>
#include <ctime>
using namespace std;

#define lson l, mid, rt << 1
#define rson mid + 1, r, rt << 1 | 1
typedef long long ll;
const int N = 1e3 + 10;
const int INF = 0x3f3f3f3f;
const int MOD = 1e9 + 7;
struct Trie {
int ch[N*30][2], sz;
int cnt[N*30];
void init(void) {
sz = 1; ch[0][0] = ch[0][1] = 0;
memset (cnt, 0, sizeof (cnt));
}
void insert(int x)  {
int u = 0;
for (int c, i=30; i>=0; --i)   {
c = x & (1 << i) ? 1 : 0;
if (!ch[u][c])  {
ch[sz][0] = ch[sz][1] = 0;
ch[u][c] = sz++;
}
u = ch[u][c];
cnt[u]++;
}
}
void remove(int x)  {
int u = 0;
for (int c, i=30; i>=0; --i)    {
c = x & (1 << i) ? 1 : 0;
u = ch[u][c];
cnt[u]--;
}
}
int query(int x)    {
int u = 0;
for (int c, i=30; i>=0; --i)   {
c = x & (1 << i) ? 1 : 0;
if (c == 1) {
if (ch[u][0] && cnt[ch[u][0]])  u = ch[u][0];
else    u = ch[u][1], x ^= (1 << i);
}
else    {
if (ch[u][1] && cnt[ch[u][1]])  u = ch[u][1], x ^= (1 << i);
else    u = ch[u][0];
}
}
return x;
}
}trie;
int a
;

int main(void)    {
int T;  scanf ("%d", &T);
while (T--) {
int n;  scanf ("%d", &n);
for (int i=1; i<=n; ++i)    {
scanf ("%d", &a[i]);
}
int ans = 0;
trie.init ();
for (int i=1; i<=n; ++i)    {
trie.insert (a[i]);
}
for (int i=1; i<=n; ++i)    {
trie.remove (a[i]);
for (int j=i+1; j<=n; ++j)  {
trie.remove (a[j]);
ans = max (ans, trie.query (a[i] + a[j]));
trie.insert (a[j]);
}
trie.insert (a[i]);
}
printf ("%d\n", ans);
}

return 0;
}