balanced-parenthesis #31

Original file line number	Diff line number	Diff line change
Expand Up		@@ -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)

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43 changes: 43 additions & 0 deletions src/_DataStructures_/Stack/balanced-parenthesis/index.js

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Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,43 @@
	/**
	Given an expression string exp , write a program to examine whether the pairs and
	the orders of "{","}","(",")","[","]" are correct in expression.

	Example:
	Input: exp = "[()]{}{[()()]()}"
	Output: true

	Input: exp = "[(])"
	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 === '{' \|\| char === '(' \|\| 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() !== '{' \|\| char === ')' && s.peek() !== '(' \|\| 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

3 changes: 3 additions & 0 deletions src/_DataStructures_/Stack/index.js

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Original file line number	Diff line number	Diff line change
Expand Up		@@ -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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