Description#
Given a string s and a dictionary of strings wordDict, return true if s can be segmented into a space-separated sequence of one or more dictionary words.
Note that the same word in the dictionary may be reused multiple times in the segmentation.
Example 1:
Input: s = "leetcode", wordDict = ["leet","code"]
Output: true
Explanation: Return true because "leetcode" can be segmented as "leet code".
Example 2:
Input: s = "applepenapple", wordDict = ["apple","pen"]
Output: true
Explanation: Return true because "applepenapple" can be segmented as "apple pen apple".
Note that you are allowed to reuse a dictionary word.
Example 3:
Input: s = "catsandog", wordDict = ["cats","dog","sand","and","cat"]
Output: false
Constraints:
1 <= s.length <= 3001 <= wordDict.length <= 10001 <= wordDict[i].length <= 20s and wordDict[i] consist of only lowercase English letters.- All the strings of
wordDict are unique.
Solutions#
Solution 1#
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| class Solution:
def wordBreak(self, s: str, wordDict: List[str]) -> bool:
words = set(wordDict)
n = len(s)
f = [True] + [False] * n
for i in range(1, n + 1):
f[i] = any(f[j] and s[j:i] in words for j in range(i))
return f[n]
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| class Solution {
public boolean wordBreak(String s, List<String> wordDict) {
Set<String> words = new HashSet<>(wordDict);
int n = s.length();
boolean[] f = new boolean[n + 1];
f[0] = true;
for (int i = 1; i <= n; ++i) {
for (int j = 0; j < i; ++j) {
if (f[j] && words.contains(s.substring(j, i))) {
f[i] = true;
break;
}
}
}
return f[n];
}
}
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| class Solution {
public:
bool wordBreak(string s, vector<string>& wordDict) {
unordered_set<string> words(wordDict.begin(), wordDict.end());
int n = s.size();
bool f[n + 1];
memset(f, false, sizeof(f));
f[0] = true;
for (int i = 1; i <= n; ++i) {
for (int j = 0; j < i; ++j) {
if (f[j] && words.count(s.substr(j, i - j))) {
f[i] = true;
break;
}
}
}
return f[n];
}
};
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| func wordBreak(s string, wordDict []string) bool {
words := map[string]bool{}
for _, w := range wordDict {
words[w] = true
}
n := len(s)
f := make([]bool, n+1)
f[0] = true
for i := 1; i <= n; i++ {
for j := 0; j < i; j++ {
if f[j] && words[s[j:i]] {
f[i] = true
break
}
}
}
return f[n]
}
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| function wordBreak(s: string, wordDict: string[]): boolean {
const words = new Set(wordDict);
const n = s.length;
const f: boolean[] = new Array(n + 1).fill(false);
f[0] = true;
for (let i = 1; i <= n; ++i) {
for (let j = 0; j < i; ++j) {
if (f[j] && words.has(s.substring(j, i))) {
f[i] = true;
break;
}
}
}
return f[n];
}
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| impl Solution {
pub fn word_break(s: String, word_dict: Vec<String>) -> bool {
let words: std::collections::HashSet<String> = word_dict.into_iter().collect();
let mut f = vec![false; s.len() + 1];
f[0] = true;
for i in 1..=s.len() {
for j in 0..i {
f[i] |= f[j] && words.contains(&s[j..i]);
}
}
f[s.len()]
}
}
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| public class Solution {
public bool WordBreak(string s, IList<string> wordDict) {
var words = new HashSet<string>(wordDict);
int n = s.Length;
var f = new bool[n + 1];
f[0] = true;
for (int i = 1; i <= n; ++i) {
for (int j = 0; j < i; ++j) {
if (f[j] && words.Contains(s.Substring(j, i - j))) {
f[i] = true;
break;
}
}
}
return f[n];
}
}
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Solution 2#
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| class Trie:
def __init__(self):
self.children: List[Trie | None] = [None] * 26
self.isEnd = False
def insert(self, w: str):
node = self
for c in w:
idx = ord(c) - ord('a')
if not node.children[idx]:
node.children[idx] = Trie()
node = node.children[idx]
node.isEnd = True
class Solution:
def wordBreak(self, s: str, wordDict: List[str]) -> bool:
trie = Trie()
for w in wordDict:
trie.insert(w)
n = len(s)
f = [False] * (n + 1)
f[n] = True
for i in range(n - 1, -1, -1):
node = trie
for j in range(i, n):
idx = ord(s[j]) - ord('a')
if not node.children[idx]:
break
node = node.children[idx]
if node.isEnd and f[j + 1]:
f[i] = True
break
return f[0]
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| class Solution {
public boolean wordBreak(String s, List<String> wordDict) {
Trie trie = new Trie();
for (String w : wordDict) {
trie.insert(w);
}
int n = s.length();
boolean[] f = new boolean[n + 1];
f[n] = true;
for (int i = n - 1; i >= 0; --i) {
Trie node = trie;
for (int j = i; j < n; ++j) {
int k = s.charAt(j) - 'a';
if (node.children[k] == null) {
break;
}
node = node.children[k];
if (node.isEnd && f[j + 1]) {
f[i] = true;
break;
}
}
}
return f[0];
}
}
class Trie {
Trie[] children = new Trie[26];
boolean isEnd = false;
public void insert(String w) {
Trie node = this;
for (int i = 0; i < w.length(); ++i) {
int j = w.charAt(i) - 'a';
if (node.children[j] == null) {
node.children[j] = new Trie();
}
node = node.children[j];
}
node.isEnd = true;
}
}
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| class Trie {
public:
vector<Trie*> children;
bool isEnd;
Trie()
: children(26)
, isEnd(false) {}
void insert(string word) {
Trie* node = this;
for (char c : word) {
c -= 'a';
if (!node->children[c]) node->children[c] = new Trie();
node = node->children[c];
}
node->isEnd = true;
}
};
class Solution {
public:
bool wordBreak(string s, vector<string>& wordDict) {
Trie trie;
for (auto& w : wordDict) {
trie.insert(w);
}
int n = s.size();
vector<bool> f(n + 1);
f[n] = true;
for (int i = n - 1; ~i; --i) {
Trie* node = ≜
for (int j = i; j < n; ++j) {
int k = s[j] - 'a';
if (!node->children[k]) {
break;
}
node = node->children[k];
if (node->isEnd && f[j + 1]) {
f[i] = true;
break;
}
}
}
return f[0];
}
};
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| type trie struct {
children [26]*trie
isEnd bool
}
func newTrie() *trie {
return &trie{}
}
func (t *trie) insert(w string) {
node := t
for _, c := range w {
c -= 'a'
if node.children[c] == nil {
node.children[c] = newTrie()
}
node = node.children[c]
}
node.isEnd = true
}
func wordBreak(s string, wordDict []string) bool {
trie := newTrie()
for _, w := range wordDict {
trie.insert(w)
}
n := len(s)
f := make([]bool, n+1)
f[n] = true
for i := n - 1; i >= 0; i-- {
node := trie
for j := i; j < n; j++ {
k := s[j] - 'a'
if node.children[k] == nil {
break
}
node = node.children[k]
if node.isEnd && f[j+1] {
f[i] = true
break
}
}
}
return f[0]
}
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| function wordBreak(s: string, wordDict: string[]): boolean {
const trie = new Trie();
for (const w of wordDict) {
trie.insert(w);
}
const n = s.length;
const f: boolean[] = new Array(n + 1).fill(false);
f[n] = true;
for (let i = n - 1; i >= 0; --i) {
let node: Trie = trie;
for (let j = i; j < n; ++j) {
const k = s.charCodeAt(j) - 97;
if (!node.children[k]) {
break;
}
node = node.children[k];
if (node.isEnd && f[j + 1]) {
f[i] = true;
break;
}
}
}
return f[0];
}
class Trie {
children: Trie[];
isEnd: boolean;
constructor() {
this.children = new Array(26);
this.isEnd = false;
}
insert(w: string): void {
let node: Trie = this;
for (const c of w) {
const i = c.charCodeAt(0) - 97;
if (!node.children[i]) {
node.children[i] = new Trie();
}
node = node.children[i];
}
node.isEnd = true;
}
}
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| public class Solution {
public bool WordBreak(string s, IList<string> wordDict) {
Trie trie = new Trie();
foreach (string w in wordDict) {
trie.Insert(w);
}
int n = s.Length;
bool[] f = new bool[n + 1];
f[n] = true;
for (int i = n - 1; i >= 0; --i) {
Trie node = trie;
for (int j = i; j < n; ++j) {
int k = s[j] - 'a';
if (node.Children[k] == null) {
break;
}
node = node.Children[k];
if (node.IsEnd && f[j + 1]) {
f[i] = true;
break;
}
}
}
return f[0];
}
}
class Trie {
public Trie[] Children { get; set; }
public bool IsEnd { get; set; }
public Trie() {
Children = new Trie[26];
IsEnd = false;
}
public void Insert(string word) {
Trie node = this;
foreach (char c in word) {
int i = c - 'a';
if (node.Children[i] == null) {
node.Children[i] = new Trie();
}
node = node.Children[i];
}
node.IsEnd = true;
}
}
|
