WDI Week 2 problems - Charlie's solutions

WDI Week 2 problems.js

// WDI Week 2 problems

// Problem 1: Factorial using recursion
function factorial(n) {
    if (n < 0) return "error"; //can't do factorial with negative numbers
    else if (n < 2) return 1; //terminal condition
    else return factorial(n - 1) * n;
}
console.log("\nfactorial");
console.log(factorial(5)); // => 120

// Problem 2: Determine whether a given string is a palindrome
function isPalindrome(string) {
    string = string.replace(/\s/g, ''); // removes all whitespaces(\s) from string
    if (string.length === 1 || string.length === 0) return true; // terminal conditions
    return (string.charAt(0) === string.charAt(string.length-1) && isPalindrome(string.slice(1,string.length-1)));
}

// solution using for loop
// function isPalindrome(string) {
//     for (var i = 0; i < Math.floor(string.length / 2); i++) {
//         if (string.charAt(i) !== string.charAt(string.length - 1 - i)) return false;
//     }
//     return true;
// }

console.log("\nPalindrome");
console.log(isPalindrome('hello'));  // => false
console.log(isPalindrome('hannah'));  // => true
console.log(isPalindrome('taco cat'));  // => true

// Problem 3: Magic Square
squares = [
[[2,7,6],[9,5,1],[4,3,8]],
[[2,7,6],[9,5,1],[4,3,9]], // not magic square
[[4,9,2],[3,5,7],[8,1,6]],
[[7,12,1,14],[2,13,8,11],[16,3,10,5],[9,6,15,4]],
[[37,78,29,70,21,62,13,54,5],[6,38,79,30,71,22,63,14,46],[47,7,39,80,31,72,23,55,15],[16,48,8,40,81,32,64,24,56],[57,17,49,9,41,73,33,65,25],[26,58,18,50,1,42,74,34,66],[67,27,59,10,51,2,43,75,35],[36,68,19,60,11,52,3,44,76],[77,28,69,20,61,12,53,4,45]]
];

//returns the sum of the diagonal from lower right corner to upper left corner
function sumDiagOne(array, col, row) {
	col = typeof col == "undefined" ? array.length-1 : col;  // if col is not passed to function, set col to array.length-1
	row = typeof row == "undefined" ? array.length-1 : row;  // if row is not passed to function, set row to array.length-1
    if (col === 0 && row === 0) return array[row][col];  // terminal condition
    return array[row][col] + sumDiagOne(array, col - 1, row - 1);
}

//returns the sum of the diagonal from upper right corner to lower left corner
function sumDiagTwo(array, col, row) {
	col = typeof col == "undefined" ? array.length-1 : col;   // if col is not passed to function, set col to array.length-1
	row = typeof row == "undefined" ? 0 : row;  // if row is not passed to function, set row to 0
    if (col === 0 && row === array.length - 1) return array[row][col];  // terminal condition
    return array[row][col] + sumDiagTwo(array, col - 1, row + 1);
}

//returns the sum of a row
function sumHoriz(array, row, col) {
	col = typeof col == "undefined" ? array.length-1 : col;  // if col is not passed to function, set col to array.length-1
    if (col === 0) return array[row][col];  // terminal condition
    return array[row][col] + sumHoriz(array, row, col - 1);
}

//returns the sum of a column
function sumVert(array, col, row) {
	row = typeof row == "undefined" ? array.length-1 : row;  // if row is not passed to function, set row to array.length-1
    if (row === 0) return array[row][col];  // terminal condition
    return array[row][col] + sumVert(array, col, row - 1);
}

//returns true if the sum of both diagonals, each row and each column are equal
function isMagic(array) {
    if (sumDiagOne(array) !== sumDiagTwo(array)) {
        console.log("diagonals don't match " + sumDiagOne(array) + " " + sumDiagTwo(array));
        return false;
    }

    for (i = 0; i < array.length; i++) {
        if (sumHoriz(array, i) !== sumDiagOne(array)) {
            console.log("row " + i + " doesn't match");
            return false;
        }
        if (sumVert(array, i) !== sumDiagOne(array)) {
            console.log("column " + i + " doesn't match");
            return false;
        }
    }
    return true;
}
console.log("\nisMagic");
console.log(isMagic([0]));  // => true
console.log(isMagic([1]));  // => false
console.log(isMagic([2]));  // => true
console.log(isMagic([3]));  // => true
console.log(isMagic([4]));  // => true


// Problem 4: Determine if an array has any duplicates
// returns true is array has duplicate elements
function hasDupes(arr) {
    for (var i = 0; i < arr.length; i++) {
        for (var j = 0; j < arr.length; j++) {
            if (arr[i] === arr[j] && i !== j) return true;
        }
    }
    return false;
}

console.log("\nhasDupes");
console.log(hasDupes([1, 2, 3, 4]));  // => false
console.log(hasDupes([12, 2, 1, 3, 4, 5, 5]));  // => true

// Problem 5: Choose-2
// returns an array of arrays with each combination of 2 elements from the elements of input array
function chooseTwo(arr) {
    var output = [];
    for (var i = 0; i < arr.length; i++) {
        for (var j = 0; j < arr.length; j++) {
            if (i !== j) output.push([arr[i], arr[j]]);
        }
    }
    return output;
}

console.log("\nchooseTwo");
console.log(chooseTwo([1, 2, 3]));  //  => [[1,2],[1,3],[2,1],[2,3],[3,1],[3,2]]
console.log(chooseTwo(['a', 'b', 'c', 'd']));  //  => [['a','b'],['a','c'],['a','d'],['b','a'],['b','c'],['b','d'],['c','a'],['c','b'],['c','d'],['d','a'],['d','b'],['d','c']]