Create 854.K-Similar-Strings.cpp

BFS/854.K-Similar-Strings/854.K-Similar-Strings.cpp

@@ -0,0 +1,54 @@
+class Solution {
+public:
+    int kSimilarity(string A, string B) 
+    {
+        if (A==B) return 0;
+
+        queue<string>q;
+        q.push(A);
+
+        int step = -1;
+        unordered_set<string>visited;
+        visited.insert(A);
+
+        while (!q.empty())
+        {
+            int len = q.size();
+            step++;
+
+            while (len--)
+            {
+                string str = q.front();
+                q.pop();
+
+                int i = 0;
+                while (str[i]==B[i])
+                    i++;
+
+                for (int j=i+1; j<str.size(); j++)
+                {
+                    if (str[j]!=B[i])
+                        continue;
+
+                    string newStr = str;
+                    swap(newStr[i], newStr[j]);
+
+                    if (newStr==B)
+                        return step+1;
+
+                    if (visited.find(newStr)==visited.end())
+                    {
+                        q.push(newStr);
+                        visited.insert(newStr);
+                    }
+
+                    //cout<<str<<": "<<newStr<<endl;
+                }
+            }
+
+        }
+
+        return -1;
+
+    }
+};