给定字符串s，请断开s，以便可以在字典中找到分区的每个子字符串。返回所需的最小休息时间。
例子：
Given a dictionary ["Cat", "Mat", "Ca",
"tM", "at", "C", "Dog", "og", "Do"]
Input : Pattern "CatMat"
Output : 1
Explanation: we can break the sentences
in three ways, as follows:
CatMat = [ Cat Mat ] break 1
CatMat = [ Ca tM at ] break 2
CatMat = [ C at Mat ] break 2 so the
output is: 1
Input : Dogcat
Output : 1
询问： Facebook
该问题的解决方案基于WordBreak Trie解决方案和级别排序图。我们开始遍历给定的模式，并开始在特里中找到模式的字符。如果我们到达一个trie的节点(叶)，从那里可以遍历一个trie(字典)的新单词，我们将级别增加1，并为trie中的其余模式字符调用搜索函数。最后，我们返回最小Break。
MinBreak(Trie, key, level, start = 0 )
.... If start == key.length()
...update min_break
for i = start to keylenght
....If we found a leaf node in trie
MinBreak( Trie, key, level+1, i )
以下是上述想法的实现
C++
// C++ program to find minimum breaks needed
// to break a string in dictionary words.
#include
using namespace std;
const int ALPHABET_SIZE = 26;
// trie node
struct TrieNode {
struct TrieNode* children[ALPHABET_SIZE];
// isEndOfWord is true if the node
// represents end of a word
bool isEndOfWord;
};
// Returns new trie node (initialized to NULLs)
struct TrieNode* getNode(void)
{
struct TrieNode* pNode = new TrieNode;
pNode->isEndOfWord = false;
for (int i = 0; i < ALPHABET_SIZE; i++)
pNode->children[i] = NULL;
return pNode;
}
// If not present, inserts the key into the trie
// If the key is the prefix of trie node, just
// marks leaf node
void insert(struct TrieNode* root, string key)
{
struct TrieNode* pCrawl = root;
for (int i = 0; i < key.length(); i++) {
int index = key[i] - 'a';
if (!pCrawl->children[index])
pCrawl->children[index] = getNode();
pCrawl = pCrawl->children[index];
}
// mark last node as leaf
pCrawl->isEndOfWord = true;
}
// function break the string into minimum cut
// such the every substring after breaking
// in the dictionary.
void minWordBreak(struct TrieNode* root,
string key, int start, int* min_Break,
int level = 0)
{
struct TrieNode* pCrawl = root;
// base case, update minimum Break
if (start == key.length()) {
*min_Break = min(*min_Break, level - 1);
return;
}
// traverse given key(pattern)
int minBreak = 0;
for (int i = start; i < key.length(); i++) {
int index = key[i] - 'a';
if (!pCrawl->children[index])
return;
// if we find a condition were we can
// move to the next word in a trie
// dictionary
if (pCrawl->children[index]->isEndOfWord)
minWordBreak(root, key, i + 1,
min_Break, level + 1);
pCrawl = pCrawl->children[index];
}
}
// Driver program to test above functions
int main()
{
string dictionary[] = { "Cat", "Mat",
"Ca", "Ma", "at", "C", "Dog", "og", "Do" };
int n = sizeof(dictionary) / sizeof(dictionary[0]);
struct TrieNode* root = getNode();
// Construct trie
for (int i = 0; i < n; i++)
insert(root, dictionary[i]);
int min_Break = INT_MAX;
minWordBreak(root, "CatMatat", 0, &min_Break, 0);
cout << min_Break << endl;
return 0;
} Java
// Java program to find minimum breaks needed
// to break a string in dictionary words.
public class Trie {
TrieNode root = new TrieNode();
int minWordBreak = Integer.MAX_VALUE;
// Trie node
class TrieNode {
boolean endOfTree;
TrieNode children[] = new TrieNode[26];
TrieNode(){
endOfTree = false;
for(int i=0;i<26;i++){
children[i]=null;
}
}
}
// If not present, inserts a key into the trie
// If the key is the prefix of trie node, just
// marks leaf node
void insert(String key){
int length = key.length();
int index;
TrieNode pcrawl = root;
for(int i = 0; i < length; i++)
{
index = key.charAt(i)- 'a';
if(pcrawl.children[index] == null)
pcrawl.children[index] = new TrieNode();
pcrawl = pcrawl.children[index];
}
// mark last node as leaf
pcrawl.endOfTree = true;
}
// function break the string into minimum cut
// such the every substring after breaking
// in the dictionary.
void minWordBreak(String key)
{
minWordBreak = Integer.MAX_VALUE;
minWordBreakUtil(root, key, 0, Integer.MAX_VALUE, 0);
}
void minWordBreakUtil(TrieNode node, String key,
int start, int min_Break, int level)
{
TrieNode pCrawl = node;
// base case, update minimum Break
if (start == key.length()) {
min_Break = Math.min(min_Break, level - 1);
if(min_BreakC#
// C# program to find minimum breaks needed
// to break a string in dictionary words.
using System;
class Trie
{
TrieNode root = new TrieNode();
int minWordBreak = int.MaxValue ;
// Trie node
public class TrieNode
{
public bool endOfTree;
public TrieNode []children = new TrieNode[26];
public TrieNode()
{
endOfTree = false;
for(int i = 0; i < 26; i++)
{
children[i] = null;
}
}
}
// If not present, inserts a key
// into the trie If the key is the
// prefix of trie node, just marks leaf node
void insert(String key)
{
int length = key.Length;
int index;
TrieNode pcrawl = root;
for(int i = 0; i < length; i++)
{
index = key[i]- 'a';
if(pcrawl.children[index] == null)
pcrawl.children[index] = new TrieNode();
pcrawl = pcrawl.children[index];
}
// mark last node as leaf
pcrawl.endOfTree = true;
}
// function break the string into minimum cut
// such the every substring after breaking
// in the dictionary.
void minWordBreaks(String key)
{
minWordBreak = int.MaxValue;
minWordBreakUtil(root, key, 0, int.MaxValue, 0);
}
void minWordBreakUtil(TrieNode node, String key,
int start, int min_Break, int level)
{
TrieNode pCrawl = node;
// base case, update minimum Break
if (start == key.Length)
{
min_Break = Math.Min(min_Break, level - 1);
if(min_Break < minWordBreak)
{
minWordBreak = min_Break;
}
return;
}
// traverse given key(pattern)
for (int i = start; i < key.Length; i++)
{
int index = key[i] - 'a';
if (pCrawl.children[index]==null)
return;
// if we find a condition were we can
// move to the next word in a trie
// dictionary
if (pCrawl.children[index].endOfTree)
{
minWordBreakUtil(root, key, i + 1,
min_Break, level + 1);
}
pCrawl = pCrawl.children[index];
}
}
// Driver code
public static void Main(String[] args)
{
String []keys = {"cat", "mat", "ca", "ma",
"at", "c", "dog", "og", "do" };
Trie trie = new Trie();
// Construct trie
int i;
for (i = 0; i < keys.Length ; i++)
trie.insert(keys[i]);
trie.minWordBreaks("catmatat");
Console.WriteLine(trie.minWordBreak);
}
}
// This code is contributed by 29AjayKumar输出：
2