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Leetcode: wordLadder II
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Leetcode: wordLadder II
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Leetcode: wordLadder II
Note: does not pass yet. 01.22.2016
class Solution {
public:
vector<vector<string>> findLadders(string beginWord, string endWord, unordered_set<string> &wordList) {
unordered_map<string,vector<string>>father;//used to record
unordered_set<string>visited;
unordered_set<string> current;
unordered_set<string> next;
current.insert(beginWord);
bool found = false;
while(!current.empty() && !found)
{
for(auto word:current) {visited.insert(word);wordList.erase(word);}
for(auto word:current) //loop over all nodes at current level.
{
string parent(word);
for(int j = 0;j<word.size();j++)
for(char c ='a';c<='z';c++)
{
if(word[j] == c) continue;
swap(c,word[j]);
if((wordList.count(word)>0||word == endWord)&&!visited.count(word))
{
cout << word << endl;
next.insert(word);
father[word].push_back(parent); //save the parents
}
if(word.compare(endWord)==0) found = true;
swap(c,word[j]);
}
}
cout << next.size() << endl;
current.clear();
swap(current,next);
}
vector<vector<string>> result;
if(found)
{
vector<string> ans;
dfs_findpath(endWord,beginWord,father,ans,result);
}
return result;
}
void dfs_findpath(string endWord,string beginWord,unordered_map<string,vector<string>>father,vector<string>&ans,vector<vector<string>> &result)
{
if(endWord == beginWord)
{
reverse(ans.begin(),ans.end());
result.push_back(ans);
reverse(ans.begin(),ans.end());
return;
}
vector<string> parents = father[endWord];
for(auto it = parents.begin();it!=parents.end();it++)
{
ans.push_back(*it);
dfs_findpath(*it,beginWord,father,ans,result);
ans.pop_back();
}
}
};