Encode and decode strings added

271_Encode and Decode Strings.cpp

@@ -0,0 +1,80 @@
+/*
+Problem link: https://leetcode.com/problems/encode-and-decode-strings/
+Solved by: emotionless
+
+Design an algorithm to encode a list of strings to a string. The encoded string is then sent over the network and is decoded back to the original list of strings.
+
+Machine 1 (sender) has the function:
+
+string encode(vector<string> strs) {
+  // ... your code
+  return encoded_string;
+}
+Machine 2 (receiver) has the function:
+vector<string> decode(string s) {
+  //... your code
+  return strs;
+}
+So Machine 1 does:
+
+string encoded_string = encode(strs);
+and Machine 2 does:
+
+vector<string> strs2 = decode(encoded_string);
+strs2 in Machine 2 should be the same as strs in Machine 1.
+
+Implement the encode and decode methods.
+
+
+
+Note:
+
+The string may contain any possible characters out of 256 valid ascii characters. Your algorithm should be generalized enough to work on any possible characters.
+Do not use class member/global/static variables to store states. Your encode and decode algorithms should be stateless.
+Do not rely on any library method such as eval or serialize methods. You should implement your own encode/decode algorithm.
+*/
+
+class Codec {
+public:
+
+    // Encodes a list of strings to a single string.
+    string encode(vector<string>& strs) {
+        string ret = "";
+        for(auto s : strs) {
+            ret += int2String(s.length()) + s;
+        }
+        return ret;
+    }
+
+    // Decodes a single string to a list of strings.
+    vector<string> decode(string s) {
+        int len = s.length();
+        vector<string> ans;
+        for(int i = 0; i < len; ) {
+            int num = string2Int(s.substr(i, 10));
+            string cur = s.substr(i+10, num);
+            i += 10 + num;
+            ans.push_back(cur);
+        }
+        return ans;
+    }
+private:
+    string int2String(int len) {
+        string ret = "0000000000";
+        int l = 9;
+        while(len) {
+            int d = len % 10;
+            ret[l--] = (char)(d + '0');
+            len /= 10;
+        }
+        return ret;
+    }
+
+    int string2Int(string str) {
+        return stoi(str);
+    }
+};
+
+// Your Codec object will be instantiated and called as such:
+// Codec codec;
+// codec.decode(codec.encode(strs));