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Commit 80d5d72

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balanced-parenthesis
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‎README.md‎

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@@ -22,6 +22,8 @@ Collection of interview questions with Unit Tests. Problems includes Data Struct
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- [Implement Queue Using Stack](src/_DataStructures_/Stack/immitate-queue-using-stack)
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- [Baseball Game](src/_DataStructures_/Stack/baseball-game)
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- [Minimum Stack](src/_DataStructures_/Stack/min-stack)
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- [Balanced Parenthesis](src/_DataStructures_/Stack/balanced-parenthesis)
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- [Queue](src/_DataStructures_/Queue)
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- [Weave](src/_DataStructures_/Queue/weave)
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/**
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Given an expression string exp , write a program to examine whether the pairs and
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the orders of "{","}","(",")","[","]" are correct in expression.
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Example:
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Input: exp = "[()]{}{[()()]()}"
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Output: true
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Input: exp = "[(])"
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Output: false
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*/
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const Stack = require('../index');
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function checkBalancedParenthesis(expression) {
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let s = new Stack();
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for (let i = 0; i < expression.length; i++) {
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const char = expression[i];
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if (char === '{' || char === '(' || char === '[') {
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//If current character is a starting bracket (‘(‘ or ‘{‘ or ‘[‘) then push it to stack
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s.push(char);
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} else {
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if (s.isEmpty()) {
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//when we have only right parenthesis or brackets in expresion
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return false;
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} else if (char === '}' && s.peek() !== '{' || char === ')' && s.peek() !== '(' || char === ']' && s.peek() !== '[') {
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return false;
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}
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//If the current character is a closing bracket (‘)’ or ‘}’ or ‘]’) then pop it from stack
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s.pop();
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}
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}
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if (s.isEmpty()) {
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//expression has balanced parenthesis
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return true;
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} else {
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return false;
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}
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}
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console.log(checkBalancedParenthesis("{()}[]")); //true
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console.log(checkBalancedParenthesis("{()}}")); //false

‎src/_DataStructures_/Stack/index.js‎

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@@ -15,6 +15,9 @@ class Stack {
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peek() {
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return this.data[this.data.length - 1];
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}
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isEmpty(){ //check if stack is empty
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return this.data.length==0;
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}
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}
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module.exports = Stack;

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