ds-algo-study/DS-n-Algos/Recursion/My-Recursion-Prac-Website/Recur-website/AUX_MATERIALS/sandbox/LOs.js

Just experimenting with publishing a package

// External Reources

// * What on Earth is Recursion ? - Computerphile
//      https://www.youtube.com/watch?v=Mv9NEXX1VHc)

// * Visulaization of the call stack (written in Python)
//      https://www.cs.usfca.edu/~galles/visualization/RecFact.html


// 

// 1. Given a recursive function, identify what is the base case and
//    the recursive case.

// 2.  Explain when a recursive solution is appropriate to solving a problem over
//     an iterative solution.

// 3. Write a recursive function that takes in a number, n, argument and 
//    calculates the n-th number of the Fibonacci sequence.

function fibonacci ( n ) {
    if ( n === 1 || n === 2 ) {
        return 1;
    }

    return fibonacci( n - 1 ) + fibonacci( n - 2 );
};

fibonacci( 4 );


// 4. Write a function that calculates a factorial recursively.

function factorial ( num ) {
    if ( num === 0 ) {
        return 1;
    }

    return num * factorial( num - 1 );
};

// factorial(3);

// 5. Write a function that calculates an exponent (positive and negative) recursively.


function exponent ( num, power ) {
    if ( power < 0 ) {
        return ( 1 / exponent( num, Math.abs( power ) ) );
    }

    if ( power === 0 ) {
        return 1
    }

    return num * exponent( num, power - 1 );
};

exponent( 3, 3 );


// 6. Write a function that sums all elements of an array recursively.

function sum ( arr ) {
    if ( arr.length === 0 ) {
        return 0;
    }
    let nextSum = sum( arr.slice( 1 ) );
    return arr[ 0 ] + nextSum;
};

sum( [ 1, 2, 3 ] );

// 7. Write a function that flattens an arbitrarily nested array into one dimension.

function flatten ( arr ) {
    let newArray = [];

    arr.forEach( function ( contents ) {
        if ( Array.isArray( contents ) ) {
            newArray.push( ...flatten( contents ) );
        } else {
            newArray.push( contents );
        }
    } );

    return newArray;
};

flatten( [ 1, [ 2, [ 3 ] ] ] );

// 8. Given a buggy recursive function that causes a
// RangeError: Maximum call stack and examples of correct behavior, debug the function.

function buggySum ( arr ) {
    if ( arr.length === 0 ) {
        return 0;
    }
    let nextSum = buggySum( arr );
    return arr[ 0 ] + nextSum;
};

// console.log(buggySum([1, 2, 3]));