[Ybtoj Chapter 9 Example 1] Prefix statistics [Trie tree]

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Problem-solving ideas

Knowledge point: dictionary tree

(Hmm, I just came to the Amway blog ^ _^)

After learning the basic operations of the dictionary tree, come back and look at this question, ah, template question. . .
First put NNStore$N$ strings in the dictionary tree, let$v\left[p\right]$ represents the number of character strings ending with node p on the dictionary tree.
Calculate the answer: we traverse the string T, the answer is${\sum }_{xϵp[T]}v[p]$
（$p\left[T\right]$ represents the set of node numbers that T has traversed on the dictionary tree)

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Code

#include<iostream>
#include<cstdio>
#include<iomanip>
#include<cstring>
#include<algorithm>
#include<cmath>
using namespace std;

char a[1000010],s[1000010];
int n,m,trie[1000010][30],v[1000010],lyx=1;

void insert(){
    
    //往字典树加入一个字符串
	int len=strlen(a+1),p=1,c=0;
	for(int i=1;i<=len;i++)
	{
    
    
		c=a[i]-'a'+1;
		if(!trie[p][c])
			trie[p][c]=++lyx;
		p=trie[p][c];
	}
	v[p]++;
//	cout<<v[p]<<" "<<p;
}

int get(){
    
    //查询
	int len=strlen(s+1),p=1,ans=0,c=0;
	for(int i=1;i<=len;i++)
	{
    
    
		c=s[i]-'a'+1;
		if(!trie[p][c])
			return ans;
		p=trie[p][c];
		ans+=v[p];
	}
	return ans;
}

int main() {
    
    
	scanf("%d%d",&n,&m);
	for(int i=1;i<=n;i++)
	{
    
    
		scanf("%s",a+1);
		insert();
	}
	for(int i=1;i<=m;i++)
	{
    
    
		scanf("%s",s+1);
		printf("%d\n",get());
	}
}