【字典树+XOR】 LibreOJ 10050 The XOR Largest Pair

最新推荐文章于 2020-11-09 21:59:23 发布

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本文介绍了一种结合字典树存储和贪心算法的方法，用于从高位选择相反数，实现高效的数值处理。通过C++代码示例，详细展示了如何构建字典树并进行查询和添加操作，以最大化目标值。

字典树存储+贪心每次从高位选相反的

//#include <iostream>
//#include <cstring>
//#include <iomanip>
//#include <algorithm>
//#include <queue>
//#include <stack>
//#include <vector>
//#include <set>
//#include <map>
//#include <cmath>
//#include <cstdio>
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
typedef __int128 bll;
const ll maxn = 1e7+100;
const ll mod = 1e9+7;
const ld pi = acos(-1.0);
const ll inf = 1e18;
const ld eps = 1e-5;
const ld e = exp(1);

ll n,trie[maxn][2],ans = -inf,cnt = 1;

void add(ll str)
{
	ll to = 1;
		
	for(ll i = 32; i >= 0; i--)
	{
		ll k = (str >> i) & 1; //str在二进制下的第i位
		
		if(trie[to][k] == 0)
		{
			cnt++;
			trie[to][k] = cnt;
		}
		
		to = trie[to][k];
	}
	return ;
}

ll query(ll str)
{
	ll res = 0,to = 1;
	
	for(ll i = 32; i >= 0; i--)
	{
		ll k = (str >> i) & 1;
		
		if(trie[to][k^1] != 0)
		{
			to = trie[to][k^1];
			res += (1 << i);
		}
		else
		{
			to = trie[to][k];
		}
	
	}
	
	return res;	
}

int main()
{	
    ios::sync_with_stdio(false);
    cin.tie(0),cout.tie(0);
		
	cin >> n;
	
	for(ll i = 1; i <= n; i++)
	{
		ll x;
		cin >> x;
		
		ans = max(ans,query(x));
		add(x);
	}
	
	cout << ans << endl;
	
	return 0;
}