143. 最大異或對——（trie）

總結

1e5，nlogn，或者n,枚舉每個，貪心在trie尋找

題目鏈接

//#pragma GCC optimize(2)
#include<bits/stdc++.h>
//typedef long long ll;
#define ull       unsigned long long
//#define int       long long
#define F           first
#define S           second
#define endl        "\n"//<<flush
#define eps         1e-6
#define base        131
#define lowbit(x)   (x&(-x))
#define PI          acos(-1.0)
#define inf         0x3f3f3f3f
#define MAXN        0x7fffffff
#define INF         0x3f3f3f3f3f3f3f3f
#define ferma(a,b)  pow(a,b-2)
#define pb          push_back
#define all(x)      x.begin(),x.end()
#define memset(a,b) memset(a,b,sizeof(a));
#define IOS         ios::sync_with_stdio(false),cin.tie(0),cout.tie(0);
using namespace std;
void file()
{
#ifdef ONLINE_JUDGE
#else
    freopen("D:/LSNU/codeforces/duipai/data.txt","r",stdin);
    //  freopen("D:/LSNU/codeforces/duipai/WA.txt","w",stdout);
#endif
}
const int N=1e5+5;
int son[N*32][2],cnt[N*32],pos,a[N];
void insert(int num)
{
    int p=0;
    for(int i=31;i>=0;i--)
    {
        int &t=son[p][num>>i&1];
        if(!t)
            t=++pos;
        p=t;
    }
}
int query(int num)
{
    int sum=0,p=0;
    for(int i=31;i>=0;i--)
    {
        int tag=num>>i&1;
        if(son[p][tag^1])
            sum+=1<<i,p=son[p][tag^1];
        else
            p=son[p][tag];
    }
    return sum;
}
signed main()
{
    IOS;
    // file();
    int n;
    cin>>n;
    for(int i=1;i<=n;i++)
        cin>>a[i],insert(a[i]);
    int ans=0;
    for(int i=1;i<=n;i++)
        ans=max(ans,query(a[i]));
    cout<<ans<<endl;
    return 0;
}