nefu 680（字典树DP）

English Game

Time Limit 1000ms Memory Limit 65536K

description

This English game is a simple English words connection game. 　　The rules are as follows: there are N English words in a dictionary, and every word has its own weight v. There is a weight if the corresponding word is used. Now there is a target string X. You have to pick some words in the dictionary, and then connect them to form X. At the same time, the sum weight of the words you picked must be the biggest.

input

There are several test cases. For each test, N (1<=n<=1000) and X (the length of x is not bigger than 10000) are given at first. Then N rows follow. Each row contains a word wi (the length is not bigger than 30) and the weight of it. Every word is composed of lowercases. No two words in the dictionary are the same.

output

For each test case, output the biggest sum weight, if you could not form the string X, output -1.

sample_input

1 aaaa 　　a 2 　　3 aaa 　　a 2 　　aa 5 　　aaa 6 　　4 abc 　　a 1 　　bc 2 　　ab 4 　　c 1 　　3 abcd 　　ab 10 　　bc 20 　　cd 30 　　3 abcd 　　cd 100 　　abc 1000 bcd 10000

sample_output

8 　　7 　　5 　　40 -1

hint

source

思路：字典树DP，dp[x+len]=max(dp[x+len,dp[x]])

#include<iostream>
#include<cstring>
#include<algorithm>
#include<cstdio>
using namespace std;
const int mm=1e4+9;
class node
{ public:
  node*next[26];
  int val;
  int word;
  node(){memset(next,NULL,sizeof(next));val=word=0;}
}root,*p;
char s[mm],ss[mm];
int dp[mm];
void ins(char*s,int val)
{

  p=&root;
  int k=0;
  while(s[k]!='\0')
  {
    if(!p->next[s[k]-'a'])
      p->next[s[k]-'a']=new node();
      p=p->next[s[k]-'a'];
      ///p->word++;
      ++k;
  }
  p->word=1;
  p->val=max(val,p->val);
}
void look(char*s,int x)
{
  p=&root;
  int k=x;
  while(s[k]!='\0'&&p->next[s[k]-'a'])
  { p=p->next[s[k]-'a'];
    ++k;
    if(p->word)
    dp[k]=max(dp[k],dp[x]+p->val);
  }
}
void free_m(node*p)
{
  for(int i=0;i<26;++i)
    if(p->next[i])
  {
    free_m(p->next[i]);
    p->next[i]=NULL;
  }
  delete p;
}
int main()
{ int n,val;
  ///freopen("data.in","r",stdin);
  ///freopen("dd.txt","w",stdout);
  while(~scanf("%d%s",&n,s))
  {
    for(int i=0;i<n;++i)
    {
      scanf("%s%d",ss,&val);
      ins(ss,val);
    }
    memset(dp,-1,sizeof(dp));
    int len=strlen(s);
    dp[0]=0;
    for(int i=0;i<len;++i)
      if(dp[i]!=-1)
    look(s,i);
    if(dp[len]!=-1)printf("%d\n",dp[len]);
    else printf("-1\n");
    node *p=&root;
    ///delete p;
    /**for(int i=0;i<26;++i)
      if(p->next[i])
      {delete p->next[i];p->next[i]=NULL;}
      */
    for(int i=0;i<26;++i)
      if(p->next[i])
    {free_m(p->next[i]);p->next[i]=NULL;}
  }
}