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/**

* Given string S and a dictionary of words words, find the number of words[i]

* that is a subsequence of S.

*

* Example :

* Input:

* S = "abcde"

* words = ["a", "bb", "acd", "ace"]

* Output: 3

* Explanation: There are three words in words that are a subsequence of

* S: "a", "acd", "ace".

*

* Note:

* All words in words and S will only consists of lowercase letters.

* The length of S will be in the range of [1, 50000].

* The length of words will be in the range of [1, 5000].

* The length of words[i] will be in the range of [1, 50].

*/

public class NumberOfMatchingSubsequences792 {

public int numMatchingSubseq(String S, String[] words) {

int res = 0;

for (String w: words) {

if (isSubsequence(w, S)) res++;

}

return res;

}

private boolean isSubsequence(String s, String t) {

int i = 0;

int j = 0;

char[] chars = s.toCharArray();

char[] chart = t.toCharArray();

while (i < chars.length && j < chart.length) {

if (chars[i] == chart[j]) {

i++;

j++;

} else {

j++;

}

}

return i == chars.length;

}

public int numMatchingSubseq2(String S, String[] words) {

LinkedList<Mover>[] map = new LinkedList[26];

for (char c = 'a'; c <= 'z'; c++) {

map[c-'a'] = new LinkedList<Mover>();

}

for (String word : words) {

map[word.charAt(0)-'a'].addLast(new Mover(word));

}

int count = 0;

for (char c : S.toCharArray()) {

LinkedList<Mover> ll = map[c-'a'];

int size = ll.size();

for (int i = 0; i < size; i++) {

Mover m = ll.removeFirst();

m.move();

if (m.hasEnded()) {

count++;

} else {

map[m.currChar()-'a'].addLast(m);

}

}

}

return count;

}

class Mover {

char[] word;

int pos = 0;

Mover (String w) {

this.word = w.toCharArray();

}

char currChar() {

return this.word[pos];

}

void move() {

this.pos++;

}

boolean hasEnded() {

return this.word.length == pos;

}

}

public int numMatchingSubseq3(String S, String[] words) {

Trie trie = constructTrie(words);

int count = 0;

for (char c : S.toCharArray()) {

Trie curr = trie.children[c-'a'];

trie.children[c-'a'] = null;

while (curr != null) {

count += curr.count;

for (int nc=0; nc<26; nc++) {

if (curr.children[nc] == null) continue;

trie.children[nc] = add(curr.children[nc], trie.children[nc]);

}

curr = curr.next;

}

}

return count;

}

private Trie add(Trie a, Trie b) {

a.next = b;

return a;

}

private Trie constructTrie(String[] words) {

Trie trie = new Trie();

for (String word: words) {

trie.add(word);

}

return trie;

}

class Trie {

Trie[] children = new Trie[26];

Trie next;

int count = 0;

void add(String word) {

add(word.toCharArray(), 0);

}

void add(char[] word, int i) {

if (word.length == i) {

this.count++;

return;

}

int idx = word[i] - 'a';

if (this.children[idx] == null) {

this.children[idx] = new Trie();

}

this.children[idx].add(word, i+1);

}

}

}