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("**********\n");
 #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-;
 const int mod = 1e9 + ;
 const int maxn =  + ;
 const int inf = 0x3f3f3f3f;
 const double pi = acos(-1.0);
 const LL INF = 0x3f3f3f3f3f3f3f3fLL;

 int t, n;
 int s[];

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

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("**********\n");
 #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-;
 const int mod = 1e9 + ;
 const int maxn =  + ;
 const int inf = 0x3f3f3f3f;
 const double pi = acos(-1.0);
 const LL INF = 0x3f3f3f3f3f3f3f3fLL;

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

 struct node{
     int cnt;
     int nxt[];

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

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

 void Trie_dele(int n){
     int now = ;
     for(int i = ; i <= ; i++) {
         a[i] = n & ;
         n >>= ;
     }
     for(int i = ;i >= ; 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 = ;
         T[].init();
         LL ans = -;
         for(int i = ; i < n; i++) {
             scanf("%d", &num[i]);
             insert(num[i]);
         }
         for(int i = ; i < n; i++) {
             Trie_dele(num[i]);
             for(int j = ; 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\n", ans);
     }
     return ;
 }