HDU1247(经典字典树)

Hat’s Words

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 11894    Accepted Submission(s): 4239

Problem Description

A hat’s word is a word in the dictionary that is the concatenation of exactly two other words in the dictionary.
You are to find all the hat’s words in a dictionary.

 

Input

Standard input consists of a number of lowercase words, one per line, in alphabetical order. There will be no more than 50,000 words.
Only one case.

 

Output

Your output should contain all the hat’s words, one per line, in alphabetical order.

 

Sample Input

a

ahat

hat

hatword

hziee

word

 

Sample Output

ahat

hatword

 题意：‘帽子’单词：由其他两个单词拼接而成。输出所有的帽子单词。字典树。

静态建树：

#include"cstdio"
#include"cstring"
using namespace std;
const int MAXN=50005;
const int N=26;
struct node{
    bool val;
    node* next[N];
};
node* root;
node memory[MAXN];
int ant;

node* create()
{
    node* p=&memory[ant++];
    for(int i=0;i<N;i++)
    {
        p->next[i]=NULL;
        p->val=false;
    }
    return p;
}

void insert(char *s)
{
    node* p=root;
    for(int i=0;s[i];i++)
    {
        int k=s[i]-'a';
        if(p->next[k]==NULL) p->next[k]=create();
        p=p->next[k];
    }
    p->val=true;//若能走到最末端,则返回true; 
}

bool search(char *s)
{
    node* p=root;
    for(int i=0;s[i];i++)
    {
        int k=s[i]-'a';
        if(p->next[k]==NULL)    return false;
        p=p->next[k];
    }
    return p->val;//若只是某个已插入单词的前缀,则返回false; 
}

int main()
{
    int cnt=0;
    root=create();
    char word[MAXN][20];
    while(scanf("%s",word[cnt])!=EOF)
    {
        //if(word[cnt][0]=='0')    break;
        insert(word[cnt]);
        cnt++;
    }
    for(int i=0;i<cnt;i++)
    {
        for(int j=1;word[i][j];j++)
        {
            char fr[20]={''};
            char re[20]={''};
            strncpy(fr,word[i],j);
            strncpy(re,word[i]+j,strlen(word[i])-j);
            if(search(fr)&&search(re))
            {
                printf("%s
",word[i]);
                break;
            }
        }
    }
    
    return 0;
}

动态建树：

#include"cstdio"
#include"cstring"
#include"cstdlib"
using namespace std;
const int MAXN=50005;
const int N=26;
struct Node{
    bool x;
    Node* next[N];
    Node()
    {
        x=false;
        for(int i=0;i<N;i++)    next[i]=NULL;
    }
};
char word[MAXN][20];
int cnt;
Node *root;
void Insert(char s[])
{
    Node *p=root;
    for(int i=0;s[i];i++)
    {
        int k=s[i]-'a';
        if(p->next[k]==NULL)    p->next[k]=new Node();
        p=p->next[k];
    }
    p->x=true;
}
bool Search(char s[])
{
    Node *p=root;
    for(int i=0;s[i];i++)
    {
        int k=s[i]-'a';
        if(p->next[k]==NULL)    return false;
        p=p->next[k];
    }
    return p->x;
}
void Del(Node *p)
{
    for(int i=0;i<N;i++)
    {
        if(p->next[i]!=NULL)
        {
            Del(p->next[i]);
        }
    }
    delete p;
}
int main()
{
    root=new Node();
    while(scanf("%s",word[cnt])!=EOF)
    {
        //if(word[cnt][0]=='0')    break;
        Insert(word[cnt]);
        cnt++;
    }
    for(int i=0;i<cnt;i++)
    {
        for(int j=1;word[i][j+1];j++)
        {
            char fr[20]={''};
            char re[20]={''};
            strncpy(fr,word[i],j);
            strncpy(re,word[i]+j,strlen(word[i])-j);
            if(Search(fr)&&Search(re))
            {
                printf("%s
",word[i]);
                break;
            }        
        }
    }
    Del(root);
    return 0;
}