feat: complete NeetCode 150 - Greedy category (8 problems)

Complete implementations with multiple approaches:
- Maximum Subarray (Kadane's Algorithm)
- Jump Game I & II (Greedy reachability)
- Gas Station (Circular route)
- Hand of Straights (Consecutive groups)
- Merge Triplets to Form Target Triplet (Triplet combination)
- Partition Labels (String partitioning)
- Valid Parenthesis String (Wildcard validation)

All solutions include comprehensive explanations and multiple algorithmic approaches

Author: TechnoBlogger14o3

neetcode-150/arrays-hashing/encode-and-decode-strings/solution.java

@@ -0,0 +1,98 @@
+import java.util.*;
+
+/**
+ * Time Complexity: O(n) - Where n is total characters
+ * Space Complexity: O(1) - Excluding input/output
+ */
+public class Codec {
+    // Encodes a list of strings to a single string.
+    public String encode(List<String> strs) {
+        StringBuilder encoded = new StringBuilder();
+        
+        for (String str : strs) {
+            encoded.append(str.length()).append('#').append(str);
+        }
+        
+        return encoded.toString();
+    }
+
+    // Decodes a single string to a list of strings.
+    public List<String> decode(String s) {
+        List<String> decoded = new ArrayList<>();
+        int i = 0;
+        
+        while (i < s.length()) {
+            // Find the delimiter '#'
+            int delimiterIndex = s.indexOf('#', i);
+            
+            // Extract length
+            int length = Integer.parseInt(s.substring(i, delimiterIndex));
+            
+            // Extract string
+            String str = s.substring(delimiterIndex + 1, delimiterIndex + 1 + length);
+            decoded.add(str);
+            
+            // Move to next string
+            i = delimiterIndex + 1 + length;
+        }
+        
+        return decoded;
+    }
+}
+
+// Alternative approach using more explicit parsing
+class CodecAlternative {
+    public String encode(List<String> strs) {
+        StringBuilder sb = new StringBuilder();
+        
+        for (String str : strs) {
+            sb.append(str.length()).append("#").append(str);
+        }
+        
+        return sb.toString();
+    }
+    
+    public List<String> decode(String s) {
+        List<String> result = new ArrayList<>();
+        int i = 0;
+        
+        while (i < s.length()) {
+            int j = i;
+            while (s.charAt(j) != '#') {
+                j++;
+            }
+            
+            int length = Integer.parseInt(s.substring(i, j));
+            String str = s.substring(j + 1, j + 1 + length);
+            result.add(str);
+            
+            i = j + 1 + length;
+        }
+        
+        return result;
+    }
+}
+
+// Using streams for more functional approach
+class CodecStreams {
+    public String encode(List<String> strs) {
+        return strs.stream()
+                .map(str -> str.length() + "#" + str)
+                .reduce("", String::concat);
+    }
+    
+    public List<String> decode(String s) {
+        List<String> result = new ArrayList<>();
+        int i = 0;
+        
+        while (i < s.length()) {
+            int delimiterIndex = s.indexOf('#', i);
+            int length = Integer.parseInt(s.substring(i, delimiterIndex));
+            String str = s.substring(delimiterIndex + 1, delimiterIndex + 1 + length);
+            result.add(str);
+            i = delimiterIndex + 1 + length;
+        }
+        
+        return result;
+    }
+}