Create WordLadder-II.cpp

Graphs/WordLadder-II.cpp

@@ -0,0 +1,55 @@
+//User function Template for C++
+
+class Solution {
+public:
+    vector<vector<string>> findSequences(string beginWord, string endWord, vector<string>& wordList) {
+        // code here
+        set<string>s(wordList.begin(),wordList.end());
+        queue<vector<string>>q;
+        q.push({beginWord});
+        vector<string>usedOnlevel;
+        usedOnlevel.push_back(beginWord);
+        int level=0;
+        vector<vector<string>>ans;
+        while(!q.empty()){
+            vector<string>vec=q.front();
+            q.pop();
+            // erase all words that has been used in the prev level to transform
+            if(vec.size()>level){
+                level++;
+                for(auto it:usedOnlevel){
+                    s.erase(it);
+                }
+            }
+
+            string word=vec.back();
+            if(word==endWord){
+                if(ans.size()==0){
+                    ans.push_back(vec);
+                }
+                else if(ans[0].size()==vec.size()){
+                    ans.push_back(vec);
+                }
+            }
+            for(int i=0;i<word.size();i++){
+                char ch=word[i];
+                for(char c='a';c<='z';c++){
+                    word[i]=c;
+                    if(s.count(word)>0){
+                        vec.push_back(word);
+                        q.push(vec);
+                        // mark as visited on the level
+                        usedOnlevel.push_back(word);
+                        vec.pop_back();
+                    }
+                }
+                word[i]=ch;
+
+            }
+
+        }
+        return ans;
+
+
+    }
+};