Chip Factory(HDU5536 + 暴力 || 01字典树）

题目链接：

　　http://acm.hdu.edu.cn/showproblem.php?pid=5536

题目：

题意：

　　对于给定的n个数，求出三个下标不同的数使得(si+sj)^sk最大。

思路：

　　由于时间给了9s，所以可以暴力过。不过还可以用01字典树艹过去，不过注意字典树里面存si查询（sj+sk），不要存（si+sj）查询sk，不然会T。

暴力代码实现如下：

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

typedef long long LL;
typedef pair<LL, LL> pll;
typedef pair<LL, int> pli;
typedef pair<int, int> pii;
typedef unsigned long long uLL;

#define lson rt<<1
#define rson rt<<1|1
#define name2str(name)(#name)
#define bug printf("**********
");
#define IO ios::sync_with_stdio(false);
#define debug(x) cout<<#x<<"=["<<x<<"]"<<endl;
#define FIN freopen("/home/dillonh/CLionProjects/in.txt","r",stdin);

const double eps = 1e-8;
const int mod = 1e9 + 7;
const int maxn = 1000 + 7;
const int inf = 0x3f3f3f3f;
const double pi = acos(-1.0);
const LL INF = 0x3f3f3f3f3f3f3f3fLL;

int t, n;
int s[1007];

int main() {
#ifndef ONLINE_JUDGE
    FIN;
#endif
    scanf("%d", &t);
    while(t--) {
        scanf("%d", &n);
        LL ans = -1;
        for(int i = 1; i <= n; i++) {
            scanf("%d", &s[i]);
        }
        for(int i = 1; i <= n; i++) {
            for(int j = 1; j < i; j++) {
                for(int k = 1; k < j; k++) {
                    ans = max(ans, (LL)(s[i] + s[j]) ^ s[k]);
                    ans = max(ans, (LL)(s[i] + s[k]) ^ s[j]);
                    ans = max(ans, (LL)(s[j] + s[k]) ^ s[i]);
                }
            }
        }
        printf("%lld
", ans);
    }
    return 0;
}

01字典树：

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

typedef long long LL;
typedef pair<LL, LL> pll;
typedef pair<LL, int> pli;
typedef pair<int, int> pii;
typedef unsigned long long uLL;

#define lson rt<<1
#define rson rt<<1|1
#define name2str(name)(#name)
#define bug printf("**********
");
#define IO ios::sync_with_stdio(false);
#define debug(x) cout<<#x<<"=["<<x<<"]"<<endl;
#define FIN freopen("/home/dillonh/CLionProjects/in.txt","r",stdin);

const double eps = 1e-8;
const int mod = 1e9 + 7;
const int maxn = 1000 + 7;
const int inf = 0x3f3f3f3f;
const double pi = acos(-1.0);
const LL INF = 0x3f3f3f3f3f3f3f3fLL;

int t, n, le, root;
int a[40], num[maxn];

struct node{
    int cnt;
    int nxt[3];

    void init(){
        cnt = 0;
        nxt[0] = nxt[1] = -1;
    }
}T[maxn*130];

void insert(int n){
    int now = root;
    for(int i = 0; i <= 30; i++) {
        a[i] = n & 1;
        n >>= 1;
    }
    for(int i = 30; i >= 0; i--){
        int x = a[i];
        if(T[now].nxt[x] == -1){
            T[le].init();
            T[now].nxt[x] = le++;
        }
        now = T[now].nxt[x];
        T[now].cnt++;
    }
}

LL search(int n){
    int now = root;
    LL ans = 0;
    for(int i = 0; i <= 30; i++) {
        a[i] = n & 1;
        n >>= 1;
    }
    for(int i = 30; i >= 0; i--){
        int x = a[i];
        if(T[now].nxt[1-x] == -1 || T[T[now].nxt[1-x]].cnt <= 0) {
            now = T[now].nxt[x];
        } else {
            ans += 1LL << i;
            now = T[now].nxt[1-x];
        }
    }
    return ans;
}

void Trie_dele(int n){
    int now = 0;
    for(int i = 0; i <= 30; i++) {
        a[i] = n & 1;
        n >>= 1;
    }
    for(int i = 30;i >= 0; i--){
        int tmp = a[i];
        now = T[now].nxt[tmp];
        T[now].cnt--;
    }
}

int main() {
#ifndef ONLINE_JUDGE
    FIN;
#endif
    scanf("%d", &t);
    while(t--) {
        scanf("%d", &n);
        le = 1;
        T[0].init();
        LL ans = -1;
        for(int i = 0; i < n; i++) {
            scanf("%d", &num[i]);
            insert(num[i]);
        }
        for(int i = 0; i < n; i++) {
            Trie_dele(num[i]);
            for(int j = 0; j < i; j++) {
                if(i == j) continue;
                Trie_dele(num[j]);
                ans = max(ans, search(num[i] + num[j]));
                insert(num[j]);
            }
            insert(num[i]);
        }
        printf("%lld
", ans);
    }
    return 0;
}