字典树

1.hdoj 1251 统计哪题

初级字典树，建树，插入，查询。

 

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;

struct Trie{
    int cnt;
    Trie* next[26];
    Trie():cnt(0){ for(int i=0; i<26; ++i) next[i] = NULL; }
}*head;

void update(char ch[]){
    int len, i;
    Trie *s, *temp;
    len = strlen(ch);
    s = head;
    for(i=0; i<len; ++i){
        if(s -> next[ch[i] - 'a'] == NULL){
            temp = new Trie;
            s -> next[ch[i] - 'a'] = temp;
        }
        s = s -> next[ch[i] - 'a'];
        (s -> cnt) ++;
    }
}

int query(char ch[]){
    int i, len, ans;
    Trie* s;
    s = head;
    len = strlen(ch);
    for(i=0; i<len; ++i){
        if(s -> next[ch[i] - 'a'] == NULL){
            return 0;
        }else{
            s = s -> next[ch[i] - 'a'];
            ans = s -> cnt;
        }
    }
    return ans;
}

void del(Trie *s){
    for(int i=0; i<26; ++i){
        if(s->next[i] != NULL)
            del(s->next[i]);
    }
    delete s;
}

int main(){
//    freopen("c:/aaa.txt", "r", stdin);
    char ch[15];
    head = new Trie;
    while(gets(ch)){
        if(strcmp(ch, "") == 0) break;
        update(ch);
    }
    while(gets(ch)){
        printf("%d\n", query(ch));
    }
    del(head);
    return 0;
}

2.hdoj 1671 Phone List

插入时，有没有遇到前一个号码，或者现在这个号码是不是之前号码的子串。 

 

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;

struct Trie{
    Trie *next[10];
    int cnt;
    bool end;
    Trie():cnt(0),end(0){ for(int i=0; i<10; ++i) next[i] = NULL; }
}*head;

bool insert(char ch[]){
    int i, j, len;
    Trie *s, *temp;

    s = head;
    len = strlen(ch);
    for(i=0; i<len; ++i){
        if(s->next[ch[i]-'0'] == NULL){
            temp = new Trie;
            s->next[ch[i]-'0'] = temp;
        }

        s = s->next[ch[i]-'0'];
        if(s->end != 0) return 0;
        if(i == len-1 && s->cnt != 0) return 0;
        s->cnt ++;
        if(i == len-1) s->end = 1;
    }
    return 1;
}

void del(Trie* s){
    int i;
    for(i=0; i<10; ++i){
        if(s->next[i] != NULL){
            del(s->next[i]);
        }
    }
    delete s;
}

int main(){
//  freopen("c:/aaa.txt", "r", stdin);
    int T, n;
    bool flag;
    char ch[100];

    scanf("%d", &T);
    while(T--){
        scanf("%d", &n);
        flag = 1;
        head = new Trie;
        while(n--){
            scanf("%s", ch);
            if(flag) flag = insert(ch);
        }
        (flag) ? puts("YES") : puts("NO");
        del(head);
    }
    return 0;
}

3.hdoj 1800 Flying to the Mars

没看见数据里还有个04，哎，看题太不仔细了。。。。

 

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;

struct Trie{
    int cnt;
    Trie *next[10];
    Trie():cnt(0){for(int i=0; i<10; ++i) next[i] = NULL; }
}*head;

int ans;

void insert(char ch[]){
    Trie *s, *temp;
    int len, i, j;
    len = strlen(ch);

    for(i=0; i<len; ++i) if(ch[i] > '0' && ch[i] <= '9') break;
    if(i == len){
        strcpy(ch, "0");
        j = 1;
    }else{
        for(j=0; i<len; ++i){
            ch[j++] = ch[i];
        }
    }

    len = j;
    s = head;
    for(i=0; i<len; ++i){
        if(s -> next[ch[i] - '0'] == NULL){
            temp = new Trie;
            s -> next[ch[i] - '0'] = temp;
        }
        s = s -> next[ch[i] - '0'];
        if(i == len-1){
            s ->cnt ++;
            if(s -> cnt > ans) ans = s -> cnt;
        }
    }
}

void del(Trie *s){
    for(int i=0; i<10; ++i){
        if(s -> next[i] != NULL)
            del(s -> next[i]);
    }
    delete s;
}

int main(){
//  freopen("c:/aaa.txt", "r", stdin);
    char ch[32];
    int n;
    while(scanf("%d", &n)!=EOF){
        ans = 0;
        head = new Trie;
        while(n--){
            scanf("%s", ch);
            insert(ch);
        }
        printf("%d\n", ans);
        del(head);
    }
    return 0;
}

4.hdoj 1247 Hat’s Words

刚开始的做法是将两个单词拼成一个单词，然后查找这个单词。而没想到将一个单词分成两个单词，

然后查找这两个单词。前一种的规模是50，000 * 50,000 * 50 ，后一种50,000 * 50 * 50。

搜索策略改一点点就很不一样呀。

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;

struct Trie{
    Trie *next[26];
    bool end;
    Trie():end(0){ for(int i=0; i<26; ++i) next[i] = NULL; }
}*head;

char str[50010][100];
int n;

void insert(char ch[]){
    int len, i;
    Trie *s, *temp;
    s = head;
    len = strlen(ch);
    for(i=0; i<len; ++i){
        if(s -> next[ch[i] - 'a'] == NULL){
            temp = new Trie;
            s -> next[ch[i] - 'a'] = temp;
        }
        s = s -> next[ch[i] - 'a'];
        if(i == len - 1){
            s -> end = 1;
        }
    }
}

bool query(char ch[]){
    int len, i;
    Trie *s;
    s = head;
    len = strlen(ch);
    for(i=0; i<len; ++i){
        if(s -> next[ch[i] - 'a'] == NULL) return 0;
        s = s -> next[ch[i] - 'a'];
        if(i == len - 1 && s -> end == 1) return 1;
    }
    return 0;
}

int main(){
//    freopen("c:/aaa.txt", "r", stdin);
    char ch1[100], ch2[100];
    int idx, i, j, k, len;
    head = new Trie;
    idx = 0;
    while(scanf("%s", &str[idx])!=EOF){
        insert(str[idx]);
        ++idx;
    }

    n = idx;
    for(i=1; i<n; ++i){
        len = strlen(str[i]);
        for(j=1; j<len; ++j){
            for(k=0; k<j; ++k){
                ch1[k] = str[i][k];
            }
            ch1[k] = '\0';

            idx = 0;
            for(k=j; k<len; ++k){
                ch2[idx++] = str[i][k];
            }
            ch2[idx] = '\0';

            if(query(ch1) && query(ch2)){
                puts(str[i]);
                break;
            }
        }
    }

    return 0;
}

5.hdoj 2846 Repository 

把“查询的字符串”构成字典树，然后查询“给出的字符串”中包含了哪些“查询的字符串”。

#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;

struct Trie {
	int end;
	Trie* next[26];
	Trie():end(-1) { for(int i=0; i<26; ++i) next[i] = NULL; }
};

Trie *head;


int n, m;
char _s[10002][22];
bool mark[100002];
int ans[100002];
int father[100002];


void insert(char ch[], int id) {
	int i, len;
	Trie *now, *temp;
	now = head;
	len = strlen(ch);
	for(i=0; i<len; ++i) {
		if(now->next[ch[i]-'a'] == NULL) {
			temp = new Trie;
			now->next[ch[i]-'a'] = temp;
		}
		now = now->next[ch[i]-'a'];
		if(i == len - 1) {
			if(now->end >= 0) father[id] = now->end;
			else now->end = id;
		}
	}
}


void query(char ch[]) {
	int i, len;
	Trie *now;
	now = head;
	len = strlen(ch);
	for(i=0; i<len; ++i) {
		if(now->next[ch[i] - 'a'] == NULL) return;
		now = now->next[ch[i] - 'a'];
		if(now->end >= 0 && mark[now->end] == 0) {
			mark[now->end] = 1;
			ans[now->end] ++;
		}
	}
}

			


void solve(int x) {
	int i, len;
	len = strlen(_s[x]);
	for(i=0; i<len; ++i) {
		query(_s[x]+i);
	}
}



void myfree(Trie *now) {
	int i;
	for(i=0; i<26; ++i) {
		if(now->next[i] != NULL) {
			myfree(now->next[i]);
			delete now->next[i];
		}
	}
}



int main() {
//	freopen("c:/aaa.txt", "r", stdin);
	int i, j;
	char ch[25];
	scanf("%d", &n);
	for(i=0; i<n; ++i) scanf("%s", _s[i]);
	
	head = new Trie;
	scanf("%d", &m);
	for(i=0; i<m; ++i) {
		ans[i] = 0;
		father[i] = i;
		scanf("%s", ch);
		insert(ch, i);
	}

	for(i=0; i<n; ++i) {
		for(j=0; j<m; ++j) mark[j] = 0;
		solve(i);
	}

	for(i=0; i<m; ++i) 
		printf("%d\n", ans[father[i]]);
	myfree(head);
	return 0;
}