Update RemoveDuplicatesFromString.java

Author: Widea

solutions/java/RemoveDuplicatesFromString.java

@@ -1,8 +1,16 @@
+// Program to remove duplicates from a given string
+// 1. getUniqueString(String) method uses a boolean array.
+// 2. removeDuplicates(String) method uses a hash map.
+// Both the methods have O(n) space and time complexity. (n being the string length)
+
+import java.util.HashMap;
+
 public class RemoveDuplicatesFromString {
 	public static void main(String[] args) {
 		RemoveDuplicatesFromString rsd = new RemoveDuplicatesFromString();
 		String input = "Tree Traversal";
-		System.out.println(rsd.getUniqueString(input));
+		System.out.println("Method 1: " +rsd.getUniqueString(input));
+		System.out.println("Method 2: " +rsd.removeDuplicates(input));
 	}
 
 	public String getUniqueString(String input) {
@@ -17,4 +25,17 @@ public String getUniqueString(String input) {
 		}
 		return sb.toString();
 	}
-}
+	
+	public String removeDuplicates(String input) {
+		HashMap<Character, Integer> map = new HashMap<>();
+		StringBuffer sb = new StringBuffer("");
+		for (int i = 0; i < input.length(); i++) {
+			char c = input.charAt(i);
+			if (!map.containsKey(c)) {
+				sb.append(c);
+				map.put(c, 1);
+			}
+		}
+		return sb.toString();
+	}
+}