Create encode-and-decode-strings.cpp

Author: kamyu104

C++/encode-and-decode-strings.cpp

@@ -0,0 +1,42 @@
+// Time:  O(n)
+// Space: O(1)
+
+class Codec {
+public:
+
+    // Encodes a list of strings to a single string.
+    string encode(vector<string>& strs) {
+        string s;
+        for (size_t i = 0; i < strs.size(); ++i) {
+            size_t len = strs[i].length();
+            string tmp;
+            for (size_t i = 0, mask = 0xff; i < sizeof(size_t); ++i, mask <<= 8) {
+                tmp.push_back(len & mask);
+            }
+            reverse(tmp.begin(), tmp.end());
+            s.append(tmp);
+            s.append(strs[i]);
+        }
+    
+        return s;
+    }
+    
+    // Decodes a single string to a list of strings.
+    vector<string> decode(string s) {
+        vector<string> strs;
+        size_t pos = 0;
+    
+        while (pos + sizeof(size_t) <= s.length()) {
+            size_t len = 0;
+            for (size_t i = 0; i < sizeof(size_t); ++i) {
+                len <<= 8;
+                len += static_cast<unsigned char>(s[pos++]);
+            } 
+    
+            strs.push_back(s.substr(pos, len));
+            pos += len;
+        }
+    
+        return strs;
+    }
+};