From 27c1240df74a6e52fe9d8f9af9dc3c90da3dd2d6 Mon Sep 17 00:00:00 2001
From: Ruoxin Zhao <rainzrx@gmail.com>
Date: Wed, 8 Dec 2021 14:09:53 -0600
Subject: [PATCH] Add the solution of LeetCode Algorithm question 127 Word
 ladder

---
 LeetCode/127.Word-ladder.cpp | 40 ++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)
 create mode 100644 LeetCode/127.Word-ladder.cpp

diff --git a/LeetCode/127.Word-ladder.cpp b/LeetCode/127.Word-ladder.cpp
new file mode 100644
index 0000000..46ff590
--- /dev/null
+++ b/LeetCode/127.Word-ladder.cpp
@@ -0,0 +1,40 @@
+class Solution {
+public:
+    int ladderLength(string beginWord, string endWord, vector<string>& wordList) {
+        //Use a typical implementation of BFS with a queue
+
+        queue<string> que1;
+        que1.push(beginWord);
+        int dist=0;
+
+        while(!que1.empty()) {
+            dist+=1;
+            int l=que1.size();
+            for(int i=0; i<l; ++i) {
+                for(vector<string>::iterator itr=wordList.begin(); itr!=wordList.end(); ++itr) {
+                    int d=wordDist(que1.front(), *itr);
+                    if(d>1) continue;
+                    if(endWord.compare(*itr)==0) return dist+1;
+                    que1.push(*itr);
+                    wordList.erase(itr);
+                    --itr;
+                }
+                que1.pop();
+            }
+        }
+
+        return 0;
+    }
+
+private:
+    //A function for computing distance between words
+    int wordDist(string s1, string s2) {
+        int n=min(s1.length(), s2.length());
+        int dist=0;
+
+        for(int i=0; i<n; ++i)
+            if(s1[i]!=s2[i]) dist+=1;
+
+        return dist;
+    }
+};