Create WordLadder-I.cpp

Graphs/WordLadder-I.cpp

@@ -0,0 +1,35 @@
+class Solution {
+public:
+    int ladderLength(string startWord, string targetWord, vector<string>& wordList) {
+        queue<pair<string,int>>q;
+        q.push({startWord,1});
+        unordered_set<string>s(wordList.begin(),wordList.end());
+        s.erase(startWord);
+        int ans=0;
+        while(!q.empty()){
+            string word=q.front().first;
+            int freq=q.front().second;
+            q.pop();
+            if(word==targetWord){
+                return freq;
+            }
+            // hat initial word
+            for(int i=0;i<word.size();i++){
+                char original=word[i];
+                // aat
+                // bat
+                // cat.......... zat
+                for(char ch='a';ch<='z';ch++){
+                    word[i]=ch;
+                    // it exists in the set
+                    if(s.find(word)!=s.end()){
+                        s.erase(word);
+                        q.push({word,freq+1});
+                    }
+                }
+                word[i]=original;
+            }
+        }
+        return 0;
+    }
+};