From 80d5d72fe200d094dd8303ee20a4f28978bda364 Mon Sep 17 00:00:00 2001
From: SumeetHaryani <sumeetharyani3@gmail.com>
Date: Sat, 5 Oct 2019 00:39:22 +0530
Subject: [PATCH] balanced-parenthesis
---
 README.md &#124; 2 +
 .../Stack/balanced-parenthesis/index.js &#124; 43 +++++++++++++++++++
 src/_DataStructures_/Stack/index.js &#124; 3 ++
 3 files changed, 48 insertions(+)
 create mode 100644 src/_DataStructures_/Stack/balanced-parenthesis/index.js
diff --git a/README.md b/README.md
index 3b441d03..c839b342 100644
--- a/README.md
+++ b/README.md
@@ -22,6 +22,8 @@ Collection of interview questions with Unit Tests. Problems includes Data Struct
 - [Implement Queue Using Stack](src/_DataStructures_/Stack/immitate-queue-using-stack)
 - [Baseball Game](src/_DataStructures_/Stack/baseball-game)
 - [Minimum Stack](src/_DataStructures_/Stack/min-stack)
+ - [Balanced Parenthesis](src/_DataStructures_/Stack/balanced-parenthesis)
+
 - [Queue](src/_DataStructures_/Queue)
 - [Weave](src/_DataStructures_/Queue/weave)
 
diff --git a/src/_DataStructures_/Stack/balanced-parenthesis/index.js b/src/_DataStructures_/Stack/balanced-parenthesis/index.js
new file mode 100644
index 00000000..01b0c0cb
--- /dev/null
+++ b/src/_DataStructures_/Stack/balanced-parenthesis/index.js
@@ -0,0 +1,43 @@
+/**
+ Given an expression string exp , write a program to examine whether the pairs and 
+ the orders of &quot;{&quot;,&quot;}&quot;,&quot;(&quot;,&quot;)&quot;,&quot;[&quot;,&quot;]&quot; are correct in expression.
+
+Example:
+Input: exp = &quot;[()]{}{[()()]()}&quot;
+Output: true
+
+Input: exp = &quot;[(])&quot;
+Output: false
+*/
+
+
+const Stack = require('../index');
+
+function checkBalancedParenthesis(expression) {
+ let s = new Stack();
+ for (let i = 0; i < expression.length; i++) {
+ const char = expression[i];
+ if (char === '{' &#124;&#124; char === '(' &#124;&#124; char === '[') {
+ //If current character is a starting bracket (‘(‘ or ‘{‘ or ‘[‘) then push it to stack
+ s.push(char);
+ } else {
+ if (s.isEmpty()) {
+ //when we have only right parenthesis or brackets in expresion
+ return false;
+ } else if (char === '}' && s.peek() !== '{' &#124;&#124; char === ')' && s.peek() !== '(' &#124;&#124; char === ']' && s.peek() !== '[') {
+ return false;
+ }
+ //If the current character is a closing bracket (‘)’ or ‘}’ or ‘]’) then pop it from stack
+ s.pop();
+ }
+ }
+ if (s.isEmpty()) {
+ //expression has balanced parenthesis
+ return true;
+ } else {
+ return false;
+ }
+}
+
+console.log(checkBalancedParenthesis("{()}[]")); //true
+console.log(checkBalancedParenthesis("{()}}")); //false
\ No newline at end of file
diff --git a/src/_DataStructures_/Stack/index.js b/src/_DataStructures_/Stack/index.js
index eb18a8ea..4836ae65 100644
--- a/src/_DataStructures_/Stack/index.js
+++ b/src/_DataStructures_/Stack/index.js
@@ -15,6 +15,9 @@ class Stack {
 peek() {
 return this.data[this.data.length - 1];
 }
+ isEmpty(){ //check if stack is empty
+ return this.data.length==0;
+ }
 }
 
 module.exports = Stack;
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