BZOJ3895 取石子

Orz PoPoQQQ

我等蒟蒻只能想到石子数 ≥ 2时的情况。。。1的时候就爆搜？大概是这个意思

最后再记忆化一下

 1 /**************************************************************
 2     Problem: 3895
 3     User: rausen
 4     Language: C++
 5     Result: Accepted
 6     Time:500 ms
 7     Memory:12524 kb
 8 ****************************************************************/
 9
10 #include <cstdio>
11 #include <cstring>
12
13 using namespace std;
14
15 int n;
16 int f[60][50005];
17
18 int dfs(int a, int b) {
19     if (!a) return b & 1;
20     if (b == 1) return dfs(a + 1, 0);
21     if (~f[a][b]) return f[a][b];
22     if ((a && !dfs(a - 1, b)) || (a && b && !dfs(a - 1, b + 1)) || (a >= 2 && !dfs(a - 2, b + 2 + (b > 0))) || (b && !dfs(a, b - 1))) return f[a][b] = 1;
23     return f[a][b] = 0;
24 }
25
26 int main() {
27     int T, i, a, b, x;
28     memset(f, -1, sizeof(f));
29     scanf("%d", &T);
30     while (T--) {
31         scanf("%d", &n);
32         for (i = 1, a = 0, b = -1; i <= n; ++i) {
33             scanf("%d", &x);
34             if (x == 1) ++a;
35             else b += x + 1;
36         }
37         if (b == -1) b = 0;
38         puts(dfs(a, b) ? "YES" : "NO");
39     }
40     return 0;
41 }