Merge pull request #437 from shraddhamishra611/master

Balanced Parenthesis

Author: smv1999

Data Structures/Stacks/BalancedParenthesis.java

@@ -0,0 +1,62 @@
+import java.util.*;
+import java.io.*;
+import java.lang.*;
+
+class BalancedParenthesis{
+	public static void main(String args[]){
+		Scanner scan = new Scanner(System.in);
+		
+		//Reading total number of testcases
+		int t = scan.nextInt();
+		while(t-->0){
+			//reading the string
+			String str = scan.next();
+			
+			//calling ispar() of Parenthesis class and printing "balanced" if it returns true else print "not balanced"
+			if(new Solution().ispar(str) == true)
+				System.out.println("balanced");
+			else
+				System.out.println("not balanced");
+		}
+	}
+}
+
+class Solution{
+	//Function to check if brackets are balanced or not.
+	static boolean ispar(String str){
+	
+	//if string is null or the length of string is not even then string is not balanced.
+        if (str == null || ((str.length() % 2) != 0)) {
+            return false;
+        } 
+        else {
+        //if string entered is other than parenthesis, return false.
+            char[] ch = str.toCharArray();
+            for (char c : ch) {
+                if (!(c == '{' || c == '[' || c == '(' || c == '}' || c == ']' || c == ')')) {
+                    return false;
+                }
+
+            }
+        }
+
+        Deque<Character> deque = new LinkedList<>();
+        //peekFirst() is used to retrieve or fetch the first element of the deque.
+        
+        for (char ch : str.toCharArray()) {
+            if (ch == '{' || ch == '[' || ch == '(') {
+                deque.addFirst(ch);
+            } 
+            else {
+                if (!deque.isEmpty() && ((deque.peekFirst() == '{' && ch == '}') || (deque.peekFirst() == '[' && ch == ']') || (deque.peekFirst() == '(' && ch == ')'))) {
+                    deque.removeFirst();
+                } 
+                else 
+                    return false;
+            }
+        }
+
+        return true;
+    }
+}
+