统计难题HDU - 1251map打表或字典树字典树模板

Posted 2022-07-29 keepz

思路

题意：题目为中文题，这里不再过多阐述。
思路1：可以在读入单词表的过程中将单词分解，用map将它一 一记录
思路2：利用字典树，这个方法较快些，下面代码中会分别给出数组和结构体指针两种形式的字典树，指针形式的有时可能会因题目内存限制而导致Memory Limit Exceeded，这时就可选择数组形式的。不过对于本题来说不用担心。

AC代码

代码1：map打表

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
map<string, int> table;
int main()

    std::ios::sync_with_stdio(false);
//    freopen("input.txt", "r", stdin);
//    freopen("output.txt", "w", stdout);
    table.clear();
    string s;
    while(getline(cin, s))
    
        if(s[0] == '\0')
            break;
        string ss = "";
        for(int i = 0; i < s.size(); i++)
        
            ss += s[i];
            table[ss]++;
        
    
    while(cin >> s)
    
        cout << table[s] << endl;
    

代码2：数组形式的字典树

#include<bits/stdc++.h>
using namespace std;
const int maxnode = 400001;
const int maxs = 27;
char s[10 + 10];
int trie[maxnode][maxs] ;
int sum[maxnode] ;
int node = 0;
void inserts(char *t)

    int len = strlen(t);
    int cur = 0;
    for(int i = 0; i < len; i++)
    
        int p = t[i] - 'a';
        if(!trie[cur][p])
            trie[cur][p] = ++node;
        sum[trie[cur][p]]++;
        cur = trie[cur][p];
    

int searchs(char *t)

    int len = strlen(t);
    int cur = 0;
    for(int i = 0; i < len; i++)
    
        int p = t[i] - 'a';
        if(!trie[cur][p])
            return 0;
        cur = trie[cur][p];
    
    return sum[cur];

int main()

//    freopen("input.txt", "r", stdin);
//    freopen("output.txt", "w", stdout);
    memset(trie, 0, sizeof(trie));
    memset(sum, 0, sizeof(sum));
    while(gets(s) != NULL)
    
        if(s[0] == '\0')
            break;
        inserts(s);
    
    while(scanf("%s", s) != EOF)
    
        cout << searchs(s) << endl;
    

代码3：结构体指针形式的字典树

//#include<bits/stdc++.h>
#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
char s[10+10];
struct Trie

    Trie* next[26];
    int sum;
    Trie()
    
        for(int i = 0; i < 26; i++)
            next[i] = NULL;
        sum = 0;
    
root;
void inserts(char *s)

    Trie* p = &root;
    int len = strlen(s);
    for(int i = 0; i < len; i++)
    
        int cur = s[i] - 'a';
        if(p->next[cur] == NULL)
        
            p->next[cur] = new Trie;
        
        p = p->next[cur];
        p->sum++;
    

int finds(char *s)

    Trie* p = &root;
    int len = strlen(s);
    for(int i = 0; i < len; i++)
    
        int cur = s[i] - 'a';
        if(p->next[cur] == NULL)
            return 0;
        else
            p = p->next[cur];
    
    return p->sum;



int main()

//    freopen("input.txt", "r", stdin);
//    freopen("output.txt", "w", stdout);
    while(gets(s) != NULL)
    
        if(s[0] == '\0')
            break;
        inserts(s);
    
    while(scanf("%s", s) != EOF)
    
        cout << finds(s) << endl;