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Commit 80a12fa

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Add Recursion Basics and Interview Questions
1 parent 61e31ff commit 80a12fa

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7 files changed

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‎Recursion/0-recursion-basics.js‎

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function Piyush() {
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return Rehana();
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}
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function Rehana() {
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return Vadant();
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}
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function Vadant() {
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return Chirag();
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}
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function Chirag() {
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return Ajay();
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}
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function Ajay() {
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// base case
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return true;
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}
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// console.log(Piyush());
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function goToLunch(person) {
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if (person === 5) return true;
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console.log(person);
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return goToLunch(person + 1);
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}
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// console.log("outcome:", goToLunch(1));
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// Loops vs Recursion
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// function multiply(arr) {
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// let product = 1;
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// for (let i = 0; i < arr.length; i++) {
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// product *= arr[i];
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// }
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// return product;
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// }
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function multiply(arr) {
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console.log(arr);
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if (arr.length <= 0) {
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return 1;
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} else return arr[arr.length - 1] * multiply(arr.slice(0, arr.length - 1));
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}
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console.log(multiply([1, 2, 3, 4]));

‎Recursion/1-factorial.js‎

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// Ques 1 : Factorial of n
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// Input: n = 5 ----->>>>> Output: 120
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function factorial(n) {
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if (n === 0) {
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return 1;
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} else return n * factorial(n - 1);
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}
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console.log(factorial(5));

‎Recursion/2-range-of-numbers.js‎

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// Ques 2 : Create an array with range of numbers
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// Input: start=1, end=5 ----->>>>> Output:
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function rangeOfNumbers(startNum, endNum) {
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if (endNum < startNum) {
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return [];
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} else {
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const numbers = rangeOfNumbers(startNum, endNum - 1);
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numbers.push(endNum);
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return numbers;
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}
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}
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// rangeOfNumbers(1,5) => [1,2,3,4,5]
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// rangeOfNumbers(1,4) => [1,2,3,4]
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// rangeOfNumbers(1,3) => [1,2,3]
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// rangeOfNumbers(1,2) => [1,2]
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// rangeOfNumbers(1,1) => [1]
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// rangeOfNumbers(1,0) => []
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// console.log(rangeOfNumbers(0, 5));

‎Recursion/3-palindrome.js‎

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// Ques 3 : Given an integer x, return true if x is a palindrome, and false otherwise.
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// Input: x = 121 ----->>>>> Output: true;
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function isPalindrome(str) {
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str = str.replace(/[^a-z0-9]/i, "").toLowerCase();
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const len = str.length;
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if (len <= 1) return true;
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if (str[0] !== str[len - 1]) return false;
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return isPalindrome(str.slice(1, -1));
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}
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console.log(isPalindrome("121"));

‎Recursion/4-fibonacci.js‎

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// Ques 4 - Fibonacci Number
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// Fibonacci Series -> 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233...
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// F(0) = 0, F(1) = 1
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// F(n) = F(n - 1) + F(n - 2), for n > 1
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// Input: n = 3 ----->>>>> Output: 2
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var fib = function (n) {
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let arr = [0, 1];
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for (let i = 2; i <= n; i++) {
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arr.push(arr[i - 2] + arr[i - 1]);
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}
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return arr[n];
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};
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function fibRecursion(n) {
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if (n <= 1) return n;
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return fibRecursion(n - 1) + fibRecursion(n - 2);
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}
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// console.log(fibRecursion(15));

‎Recursion/5-reverse-string.js‎

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// Ques 5 - Reverse a String
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// Input: "hello" ----->>>>> Output: "olleh"
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function reverseString(str) {
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if (str === "") {
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return "";
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} else return reverseString(str.substr(1)) + str.charAt(0);
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}
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// console.log(reverseString("hello")); => olleh

‎Recursion/6-subsets.js‎

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// Ques 6 - Subsets ( Backtracking Algorithm using Recursion )
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// Given an integer array nums of unique elements, return all possible subsets (the power set).
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// The solution set must not contain duplicate subsets. Return the solution in any order.
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// Input: [1,2,3] ----->>>>> Output: [[],[1],[2],[1,2],[3],[1,3],[2,3],[1,2,3]]
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// Input: [0] ----->>>>> Output: [[],[0]]
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function subsets(nums) {
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let result = [];
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let temp = [];
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function recursiveSubsets(nums, i) {
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if (i === nums.length) {
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return result.push([...temp]);
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}
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temp.push(nums[i]);
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recursiveSubsets(nums, i + 1);
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temp.pop();
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recursiveSubsets(nums, i + 1);
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}
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recursiveSubsets(nums, 0);
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return result;
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}
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console.log(subsets([1]));

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