计数DP

 1 #include <bits/stdc++.h>
 2 #include <iostream>
 3 #include <algorithm>
 4 #include <cstdio>
 5 #include <cstring>
 6 #include <string>
 7 #include <cmath>
 8 #include <cstdlib>
 9 #include <queue>
10 #include <stack>
11 #include <map>
12 #include <vector>
13 #include <set>
14 #include <bitset>
15 #include <iomanip>
16 #define ms(a, b) memset(a, b, sizeof(a));
17 using namespace std;
18 typedef long long LL;
19 typedef pair<int, int> pii;
20 const int INF = 0x3f3f3f3f;
21 const int maxn = 1030;
22 const int MAXN = 2e4 + 10;
23 const double eps = 1e-8;
24 const LL mod = 1e9 + 7;
25 int a[maxn];
26 LL dp1[maxn][maxn], dp2[maxn][maxn], dp3[maxn][maxn];
27 LL ans;
28 int n;
29 
30 void solve() {
31     dp1[0][a[0]] = 1;
32     for(int i = 1; i < n - 1; i++) {
33         dp1[i][a[i]]++;
34         for(int j = 0; j < maxn; j++) {
35             if(dp1[i-1][j]) {
36                 dp1[i][j] += dp1[i-1][j];
37                 dp1[i][j] %= mod;
38                 dp1[i][j^a[i]] += dp1[i-1][j];
39                 dp1[i][j^a[i]] %= mod;
40             }
41         }
42     }
43     dp2[n-1][a[n-1]] = 1;
44     dp3[n-1][a[n-1]] = 1;
45     for(int i = n - 2; i > 0; i--) {
46         dp2[i][a[i]]++;
47         dp3[i][a[i]]++;
48         for(int j = 0; j < maxn; j++) {
49             if(dp2[i+1][j]) {
50                 dp2[i][j] += dp2[i+1][j];
51                 dp2[i][j] %= mod;
52                 dp2[i][j&a[i]] += dp2[i+1][j];
53                 dp2[i][j&a[i]] %= mod;
54                 dp3[i][j&a[i]] += dp2[i+1][j];
55                 dp3[i][j&a[i]] %= mod;
56             }
57         }
58     }
59     for(int i = 0; i < n - 1; i++) {
60         for(int j = 0; j < maxn; j++) {
61             if(dp1[i][j] && dp3[i+1][j]) {
62 //                cout << i << " " << j << " " << dp1[i][j] << " " << dp3[i+1][j] << endl;
63                 ans = (ans + dp1[i][j] * dp3[i+1][j] % mod) % mod;
64             }
65         }
66     }
67     printf("%lld\n", ans);
68 }
69 
70 int main()
71 {
72 #ifdef local
73     freopen("case.in","r",stdin);
74 //    freopen("out.in","w",stdout);
75 #endif
76     int T;
77     scanf("%d", &T);
78     while(T--) {
79         scanf("%d", &n);
80         ms(dp1, 0);
81         ms(dp2, 0);
82         ms(dp3, 0);
83         for(int i = 0; i < n; i++) {
84             scanf("%d", &a[i]);
85         }
86         ans = 0;
87         solve();
88     }
89     return 0;
90 }