Update and rename decode_string.py to decode_string.cpp

Author: avidLearnerInProgress

decode_string.cpp

@@ -0,0 +1,71 @@
+# Non recursive solution    
+# class Solution:
+#     def decodeString(self, s: str) -> str:
+#         prevStr, currStr, currNum = '', '', 0
+#         decode, ans = [], ''
+#         for ch in s:
+#             if ch == '[':
+#                 decode.append(currNum)
+#                 decode.append(currStr)
+#                 currStr = ''
+#                 currNum = 0
+#             elif ch == ']':
+#                 prevStr = decode.pop()
+#                 digit = decode.pop()
+#                 currStr = prevStr + (currStr * digit)
+#             elif ch.isdigit():
+#                 currNum = currNum * 10 + int(ch)
+#             else:
+#                 currStr += ch            
+#         return currStr
+
+    
+class Solution {
+    
+private:
+    string decodeStringHelper(int &position, string s) {
+        
+        int num = 0; //keep track of current integer
+        string word = ""; //current word 
+        
+        for(;position<s.size(); ++position) {
+            
+            //if we encounter a [ - treat it as a start of subproblem and recurse. After this repeat the substr formed from recursion num times
+            // ] - end of subproblem, return word
+            //if we encounter a number - form the num
+            //if we encounter a character - just add it to the current word 
+            
+            char currChar = s[position];
+            if(currChar == '[') {
+                string currStr = decodeStringHelper(++position, s);
+                for(; num > 0; num--) word += currStr;
+            } 
+            
+            else if(currChar >= '0' and currChar <= '9') {
+                num = num * 10 + currChar - '0';
+            }
+            
+            else if(currChar == ']') {
+                return word;
+            }
+            
+            else {
+                word += currChar;
+            }
+            
+        }
+        return word;
+    }
+    
+public:
+    /*
+        Recursive solution - more intuitive
+    */   
+    string decodeString(string s) {
+        
+        int position = 0;
+        return decodeStringHelper(position, s);
+    }
+};
+    
+