D. Recovering BST Codeforces Round #505 (rated, Div. 1 + Div. 2, based on VK Cup 2018 Final)

http://codeforces.com/contest/1025/problem/D

 

树 dp 优化

　　f[x][y][0]=f[x][z][1] & f[z+1][y][0] ( gcd(a[x-1],a[z])<>0 )

　　f[x][y][1]=f[x][z][1] & f[z+1][y][0] ( gcd(a[z],a[y+1])<>0 )

 

 1 #include <cstdio>
 2 #include <cstdlib>
 3 #include <cmath>
 4 #include <cstring>
 5 #include <time.h>
 6 #include <string>
 7 #include <set>
 8 #include <map>
 9 #include <list>
10 #include <stack>
11 #include <queue>
12 #include <vector>
13 #include <bitset>
14 #include <ext/rope>
15 #include <algorithm>
16 #include <iostream>
17 using namespace std;
18 #define ll long long
19 #define minv 1e-6
20 #define inf 1e9
21 #define pi 3.1415926536
22 #define E  2.7182818284
23 const ll mod=1e9+7;//998244353
24 const int maxn=1e3+10;
25 
26 int a[maxn];
27 bool vis[maxn][maxn]={0},f[maxn][maxn][2]={0};
28 
29 int main()
30 {
31     int n,i,j,x,y,z;
32     scanf("%d",&n);
33     for (i=1;i<=n;i++)
34         scanf("%d",&a[i]);
35     for (i=1;i<n;i++)
36         for (j=i+1;j<=n;j++)
37             vis[i][j]=(__gcd(a[i],a[j])!=1);
38     for (i=0;i<=n;i++)
39         vis[0][i]=1,vis[i][n+1]=1;
40     for (i=1;i<=n+1;i++)
41         f[i][i-1][0]=f[i][i-1][1]=1;
42     for (i=1;i<=n;i++)
43         for (x=1,y=i;x<=n-i+1;x++,y++)
44             for (z=x;z<=y;z++)
45                 if (f[x][z-1][1] && f[z+1][y][0])
46                 {
47                     if (vis[x-1][z])
48                         f[x][y][0]=1;
49                     if (vis[z][y+1])
50                         f[x][y][1]=1;
51                 }
52     if (f[1][n][0])
53         printf("Yes");
54     else
55         printf("No");
56     return 0;
57 }

 

posted @ 2018-08-24 17:16  congmingyige  阅读(148)  评论(0)  编辑  收藏  举报