Merge pull request #1682 from Abhinavcode13/patch-40

Create MaxConcatenatedstr.java

Author: akgmage

Strings/MaxConcatenatedstr.java

@@ -0,0 +1,47 @@
+class Solution {
+public:
+    // i: arr[i] we are currently looking at
+	// mask: Bitmask that represents all the characters that have been added to the current string
+	// If 0-th bit in mask is set, it means that we have added "a" in the current string
+    int solve(vector<string> &arr, int i, int mask) {
+        int n = arr.size();
+        
+        if (i >= n)
+            return 0;
+        
+        // Skip concatenating arr[i]
+        int curRes = solve(arr, i+1, mask)
+		
+		// Mask to keep track of the characters that are present in arr[i]
+		int curMask = 0;
+        
+        // Check whether any character in arr[i] is present in current string, i.e. 
+		// Check whether (arr[i]-'a')-th bit is set in mask
+        // If any existing character's bit is set, it means that we cannot concatenate arr[i]
+        // to the given string and so return curRes only which contains the result of skipping arr[i]
+        // Also, use curMask to maintain the characters in arr[i] that have been seen.
+		// It is possible that arr[i] itself has duplicate characters in which case, we will not be able to concatenate arr[i]
+        // So check whether (c-'a')-th bit is set in curMask and after that set the (c-'a')-th bit in curMask
+        for (char &c: arr[i]) {
+            if (mask & (1 << (c - 'a')))
+                return curRes;
+            
+            if (curMask & (1 << (c - 'a')))
+                return curRes;
+            
+            curMask |= (1 << (c - 'a'));
+        }
+        
+        // All the bits that were set in curMask will be now set in mask, 
+		// in order to add all characters of arr[i] to the current string
+        mask |= curMask;
+        
+        // We make a call to i+1 with the updated mask and arr[i]'s length being added
+        curRes = max(curRes, (int) arr[i].length() + solve(arr, i+1, mask));
+        return curRes;
+    }
+    
+    int maxLength(vector<string>& arr) {
+        return solve(arr, 0, 0);
+    }
+};