5353
5454** 方法一:前缀树**
5555
56+ 我们定义一棵前缀树,前缀树每个节点有两个属性,一个是长度为 26ドル$ 的子节点数组 ` children ` ,另一个是是否为单词结尾的标记 ` isEnd ` 。
57+ 58+ 我们遍历 ` words ` ,对于每个单词 ` w ` ,我们从根节点开始遍历,如果当前节点的子节点数组中没有 ` w ` 的第一个字符,我们就创建一个新的节点,然后继续遍历 ` w ` 的下一个字符,直到遍历完 ` w ` ,我们将当前节点的 ` isEnd ` 标记为 ` true ` 。
59+ 60+ 接下来我们遍历 ` words ` ,对于每个单词 ` w ` ,我们从根节点开始遍历,如果当前节点的子节点数组的 ` isEnd ` 字段为 ` false ` ,说明 ` w ` 的某个前缀不在 ` words ` 中,我们返回 ` false ` 。否则继续遍历 ` w ` 的下一个字符,直到遍历完 ` w ` ,我们返回 ` true ` 。
61+ 62+ 时间复杂度 $O(\sum_ {w \in words} |w|),ドル空间复杂度 $O(\sum_ {w \in words} |w|)$。
63+ 5664<!-- tabs:start -->
5765
5866### ** Python3**
6169
6270``` python
6371class Trie :
72+ __slots__ = [" children" " is_end"
73+ 6474 def __init__ (self
65- self .children = [None ] * 26
66- self .is_end = False
75+ self .children: List[Trie | None ] = [None ] * 26
76+ self .is_end: bool = False
6777
68- def insert (self w ) :
78+ def insert (self w : str ) -> None :
6979 node = self
7080 for c in w:
7181 idx = ord (c) - ord (" a"
72- if node.children[idx]is None :
82+ if not node.children[idx]:
7383 node.children[idx] = Trie()
7484 node = node.children[idx]
7585 node.is_end = True
7686
77- def search (self w ) :
87+ def search (self w : str ) -> bool :
7888 node = self
7989 for c in w:
8090 idx = ord (c) - ord (" a"
@@ -91,9 +101,7 @@ class Solution:
91101 trie.insert(w)
92102 ans = " "
93103 for w in words:
94- if ans and (len (ans) > len (w) or (len (ans) == len (w) and ans < w)):
95- continue
96- if trie.search(w):
104+ if (len (w) > len (ans) or len (w) == len (ans) and w < ans) and trie.search(w):
97105 ans = w
98106 return ans
99107```
@@ -104,26 +112,29 @@ class Solution:
104112
105113``` java
106114class Trie {
107- Trie [] children = new Trie [26 ];
108- boolean isEnd;
115+ private Trie [] children = new Trie [26 ];
116+ private boolean isEnd;
117+ 118+ public Trie () {
119+ }
109120
110- void insert (String w ) {
121+ public void insert (String w ) {
111122 Trie node = this ;
112123 for (char c : w. toCharArray()) {
113- c -= ' a'
114- if (node. children[c ] == null ) {
115- node. children[c ] = new Trie ();
124+ int idx = c - ' a'
125+ if (node. children[idx ] == null ) {
126+ node. children[idx ] = new Trie ();
116127 }
117- node = node. children[c ];
128+ node = node. children[idx ];
118129 }
119130 node. isEnd = true ;
120131 }
121132
122- boolean search (String w ) {
133+ public boolean search (String w ) {
123134 Trie node = this ;
124135 for (char c : w. toCharArray()) {
125- c -= ' a'
126- node = node. children[c ];
136+ int idx = c - ' a'
137+ node = node. children[idx ];
127138 if (! node. isEnd) {
128139 return false ;
129140 }
@@ -140,12 +151,8 @@ class Solution {
140151 }
141152 String ans = " "
142153 for (String w : words) {
143- if (! " " . equals(ans)
144- && (ans. length() > w. length()
145- || (ans. length() == w. length() && ans. compareTo(w) < 0 ))) {
146- continue ;
147- }
148- if (trie. search(w)) {
154+ if ((w. length() > ans. length() || (w. length() == ans. length() && w. compareTo(ans) < 0 ))
155+ && trie. search(w)) {
149156 ans = w;
150157 }
151158 }
@@ -159,30 +166,34 @@ class Solution {
159166``` cpp
160167class Trie {
161168private:
162- vector< Trie* > children;
163- bool isEnd;
169+ Trie* children[ 26 ] ;
170+ bool isEnd = false ;
164171
165172public:
166- Trie()
167- : children(26)
168- , isEnd(false) { }
173+ Trie() {
174+ fill(begin( children), end(children), nullptr);
175+ }
169176
170- void insert(string word ) {
177+ void insert(const string& w ) {
171178 Trie* node = this;
172- for (char c : word) {
173- c -= 'a';
174- if (!node->children[c]) node->children[c] = new Trie();
175- node = node->children[c];
179+ for (char c : w) {
180+ int idx = c - 'a';
181+ if (!node->children[idx]) {
182+ node->children[idx] = new Trie();
183+ }
184+ node = node->children[idx];
176185 }
177186 node->isEnd = true ;
178187 }
179188
180- bool search (string word ) {
189+ bool search (const string& w ) {
181190 Trie* node = this;
182- for (char c : word) {
183- c -= 'a';
184- node = node->children[ c] ;
185- if (!node->isEnd) return false;
191+ for (char c : w) {
192+ int idx = c - 'a';
193+ node = node->children[ idx] ;
194+ if (!node->isEnd) {
195+ return false;
196+ }
186197 }
187198 return true;
188199 }
@@ -191,12 +202,15 @@ public:
191202class Solution {
192203public:
193204 string longestWord(vector<string >& words) {
194- Trie* trie = new Trie();
195- for (auto w : words) trie->insert(w);
205+ Trie trie;
206+ for (const string& w : words) {
207+ trie.insert(w);
208+ }
196209 string ans = "";
197- for (auto w : words) {
198- if (ans != "" && (ans.size() > w.size() || (ans.size() == w.size() && ans < w))) continue;
199- if (trie->search(w)) ans = w;
210+ for (const string& w : words) {
211+ if ((w.size() > ans.size() || (w.size() == ans.size() && w < ans)) && trie.search(w)) {
212+ ans = w;
213+ }
200214 }
201215 return ans;
202216 }
@@ -214,22 +228,24 @@ type Trie struct {
214228func newTrie() *Trie {
215229 return &Trie{}
216230}
217- func (this *Trie) insert(word string) {
218- node := this
219- for _, c := range word {
220- c -= 'a'
221- if node.children[c] == nil {
222- node.children[c] = newTrie()
231+
232+ func (t *Trie) insert(w string) {
233+ node := t
234+ for _, c := range w {
235+ idx := c - 'a'
236+ if node.children[idx] == nil {
237+ node.children[idx] = newTrie()
223238 }
224- node = node.children[c ]
239+ node = node.children[idx ]
225240 }
226241 node.isEnd = true
227242}
228- func (this *Trie) search(word string) bool {
229- node := this
230- for _, c := range word {
231- c -= 'a'
232- node = node.children[c]
243+
244+ func (t *Trie) search(w string) bool {
245+ node := t
246+ for _, c := range w {
247+ idx := c - 'a'
248+ node = node.children[idx]
233249 if !node.isEnd {
234250 return false
235251 }
@@ -244,17 +260,170 @@ func longestWord(words []string) string {
244260 }
245261 ans := ""
246262 for _, w := range words {
247- if ans != "" && (len(ans) > len(w) || (len(ans) == len(w) && ans < w)) {
248- continue
249- }
250- if trie.search(w) {
263+ if (len(w) > len(ans) || (len(w) == len(ans) && w < ans)) && trie.search(w) {
251264 ans = w
252265 }
253266 }
254267 return ans
255268}
256269```
257270
271+ ### ** TypeScript**
272+ 273+ ``` ts
274+ class Trie {
275+ private children: (Trie | null )[] = Array (26 ).fill (null );
276+ private isEnd: boolean = false ;
277+ 278+ insert(w : string ): void {
279+ let node: Trie = this ;
280+ for (const of w ) {
281+ const : number = c .charCodeAt (0 ) - ' a' charCodeAt (0 );
282+ if (! node .children [idx ]) {
283+ node .children [idx ] = new Trie ();
284+ }
285+ node = node .children [idx ] as Trie ;
286+ }
287+ node .isEnd = true ;
288+ }
289+ 290+ search(w : string ): boolean {
291+ let node: Trie = this ;
292+ for (const of w ) {
293+ const : number = c .charCodeAt (0 ) - ' a' charCodeAt (0 );
294+ node = node .children [idx ] as Trie ;
295+ if (! node .isEnd ) {
296+ return false ;
297+ }
298+ }
299+ return true ;
300+ }
301+ }
302+ 303+ function longestWord(words : string []): string {
304+ const : Trie = new Trie ();
305+ for (const of words ) {
306+ trie .insert (w );
307+ }
308+ let ans: string = ' '
309+ for (const of words ) {
310+ if ((w .length > ans .length || (w .length === ans .length && w < ans )) && trie .search (w )) {
311+ ans = w ;
312+ }
313+ }
314+ return ans ;
315+ }
316+ ```
317+ 318+ ### ** Rust**
319+ 320+ ``` rust
321+ struct Trie {
322+ children : [Option <Box <Trie >>; 26 ],
323+ is_end : bool ,
324+ }
325+ 326+ impl Trie {
327+ fn new () -> Self {
328+ Trie {
329+ children : Default :: default (),
330+ is_end : false ,
331+ }
332+ }
333+ 334+ fn insert (& mut self , w : & str ) {
335+ let mut node = self ;
336+ for c in w . chars () {
337+ let idx = (c as usize ) - ('a' as usize );
338+ node = node . children[idx ]. get_or_insert_with (|| Box :: new (Trie :: new ()));
339+ }
340+ node . is_end = true ;
341+ }
342+ 343+ fn search (& self , w : & str ) -> bool {
344+ let mut node = self ;
345+ for c in w . chars () {
346+ let idx = (c as usize ) - ('a' as usize );
347+ if let Some (next_node ) = & node . children[idx ] {
348+ node = next_node . as_ref ();
349+ if ! node . is_end {
350+ return false ;
351+ }
352+ }
353+ }
354+ true
355+ }
356+ }
357+ 358+ impl Solution {
359+ pub fn longest_word (words : Vec <String >) -> String {
360+ let mut trie = Trie :: new ();
361+ for w in & words {
362+ trie . insert (w );
363+ }
364+ let mut ans = String :: new ();
365+ for w in & words {
366+ if (w . len () > ans . len () || (w . len () == ans . len () && w < & ans )) && trie . search (w ) {
367+ ans = w . clone ();
368+ }
369+ }
370+ ans
371+ }
372+ }
373+ ```
374+ 375+ ### ** C#**
376+ 377+ ``` cs
378+ public class Trie {
379+ private Trie [] children = new Trie [26 ];
380+ private bool isEnd ;
381+ 382+ public Trie () { }
383+ 384+ public void Insert (string w ) {
385+ Trie node = this ;
386+ foreach (char c in w .ToCharArray ()) {
387+ int idx = c - 'a' ;
388+ if (node .children [idx ] == null ) {
389+ node .children [idx ] = new Trie ();
390+ }
391+ node = node .children [idx ];
392+ }
393+ node .isEnd = true ;
394+ }
395+ 396+ public bool Search (string w ) {
397+ Trie node = this ;
398+ foreach (char c in w .ToCharArray ()) {
399+ int idx = c - 'a' ;
400+ node = node .children [idx ];
401+ if (! node .isEnd ) {
402+ return false ;
403+ }
404+ }
405+ return true ;
406+ }
407+ }
408+ 409+ public class Solution {
410+ public string LongestWord (string [] words ) {
411+ Trie trie = new Trie ();
412+ foreach (string w in words ) {
413+ trie .Insert (w );
414+ }
415+ 416+ string ans = " "
417+ foreach (string w in words ) {
418+ if ((w .Length > ans .Length || (w .Length == ans .Length && string .Compare (w , ans ) < 0 )) && trie .Search (w )) {
419+ ans = w ;
420+ }
421+ }
422+ return ans ;
423+ }
424+ }
425+ ```
426+ 258427### ** ...**
259428
260429```
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