hdu1521(字典树模板)

题目链接: http://acm.hdu.edu.cn/showproblem.php?pid=1251

题意: 中文题诶~

思路: 字典树模板

代码1: 动态内存, 比较好理解一点, 不过速度略慢, 代码略长

#include <iostream>
#include <stdio.h>
#include <string.h>
using namespace std;

const int MAXN = 26;
const int MAX = 11;
char str[MAX];

struct node{
    int count;
    node *next[MAXN];
    node(){
        count = 0;
        for(int i = 0; i < MAXN; i++){
            next[i] = NULL;
        }
    }
};

void insert(node *p, char *str){
    for(int i = 0; str[i] != ''; i++){
        int cnt = str[i] - 'a';
        if(p -> next[cnt] == NULL) p -> next[cnt] = new node();
        p = p -> next[cnt];
        p -> count++;
    }
}

int query(node *p, char *str){
    for(int i = 0; str[i] != ''; i++){
        int cnt = str[i] - 'a';
        p = p -> next[cnt];
        if(!p) return 0;
    }
    return p -> count;
}

void Free(node *p){
    if(!p) return;
    for(int i = 0; i < MAXN; i++){
        if(p -> next[i]) Free(p -> next[i]);
    }
    free(p);
}

int main(void){
    node *root = new node();
    while(gets(str) && str[0] != ''){
        insert(root, str);
    }
    while(gets(str)){
        printf("%d
", query(root, str));
    }
    Free(root);//本题为单组输入,不释放空间也没影响
    return 0;
}

代码2: 用数组模拟, 相对代码1略微难理解一点

#include <iostream>
#include <stdio.h>
#include <string.h>
using namespace std;

const int MAXN = 1e5 + 10;
int trie[MAXN << 2][26], sum[MAXN << 2], num = 1;
char str[11];
//每个num对应一个节点,sum[i]为i出现的次数,trie[node][cnt]存储node这条链cnt节点后一个节点的位置,并标记当前节点是否存在

void insert(void){
    int node = 0, indx = 0;
    while(str[indx]){
        int cnt = str[indx++] - 'a';
        if(!trie[node][cnt]) trie[node][cnt] = num++;
        sum[trie[node][cnt]]++;
        node = trie[node][cnt];
    }
}

int query(void){
    int node = 0, indx = 0;
    while(str[indx]){
        int cnt = str[indx++] - 'a';
        if(!trie[node][cnt]) return 0;
        node = trie[node][cnt];
    }
    return sum[node];
}

int main(void){
    while(gets(str) && str[0] != ''){
        insert();
    }
    while(gets(str)){
        printf("%d
", query());
    }
    return 0;
}