JSAlgorithm

Spiral Matrix

Ronald — Thu, 04 Jun 2020 01:11:55 +0000

function spiralMatrix(dimension) {

    let matrix = [];
    // create blank matrix based from given dimension
    for (let i = 0; i < dimension; i++) {
        matrix.push(new Array(dimension).fill(0))
    }

    let counter = 1;
    let startRow = 0, endRow = dimension, startColumn = 0, endColumn = dimension;


    while (startRow < endRow && startColumn < endColumn) {

        // top left -> top right
        for (let i = startColumn; i < endColumn; i++) {
            matrix[startRow][i] = counter++;
        }
        startRow++

        // top right -> bottom right
        for (let i = startRow; i < endRow; i++) {
            matrix[i][endColumn - 1] = counter++;
        }
        endColumn--;

        // bottom right -> bottom left
        for (let i = endColumn - 1; i >= startColumn; i--) {
            matrix[endRow - 1][i] = counter++;
        }
        endRow--;


        // bottom left -> top left
        for (let i = endRow; i > startRow; i--) {
            matrix[i - 1][startColumn] = counter++;
        }
        startColumn++;

    }

     return matrix;
}

Algorithms in JavaScript – Full Course for Beginners

Ronald — Thu, 21 May 2020 12:04:32 +0000

httpss://www.youtube.com/watch?v=t2CEgPsws3U

Game Of Life (Optimized)

Ronald — Thu, 21 May 2020 02:46:57 +0000

let gameOfLife = function(board) {

    if (!board) return [];

    let LIVE = 1,
        DEAD = 0,
        ALIVE_TO_DEAD = 0b01, // [next state, current state]
        ALIVE_TO_ALIVE = 0b11,
        DEAD_TO_ALIVE = 0b10,
        DEAD_TO_DEAD = 0b00,
        maxRow = board.length - 1,
        maxCol = board[0].length - 1;

    function getAdjacentCount(row, col, valueToCompare) {
        let sum = 0;
        for (let i = Math.max(row - 1, 0); i <= Math.min(row + 1, maxRow); i++) {
            for (let j = Math.max(col - 1, 0); j <= Math.min(col + 1, maxCol); j++) {
                if (i === row && j === col) continue;
                if (board[i][j] & 1 === valueToCompare) sum = sum + 1;
            }
        }
        return sum;
    }

    function getNextValue(row, col) {
        const val = board[row][col];
        let liveNeighbors = getAdjacentCount(row, col, LIVE);
        if (val === LIVE) {

            // Any live cell with fewer than two live neighbors dies, as if caused by under-population.
            // Any live cell with more than three live neighbors dies, as if by over-population..
            if (liveNeighbors < 2 || liveNeighbors > 3) {
                return ALIVE_TO_DEAD;
            }
            // Any live cell with two or three live neighbors lives on to the next generation.
            return ALIVE_TO_ALIVE;
        }
        // cell is DEAD
        else {
            // Any dead cell with exactly three live neighbors becomes a live cell, as if by reproduction.
            if (liveNeighbors === 3) {
                return DEAD_TO_ALIVE;
            }
            // no condition
            return DEAD_TO_DEAD;
        }
    }

    for (let row = 0; row <= maxRow; row++) {
        for (let col = 0; col <= maxCol;col++) {
            board[row][col] = getNextValue(row, col);
        }
    }

    for (let row = 0; row <= maxRow; row++) {
        for (let col = 0; col <= maxCol;col++) {
            board[row][col] = board[row][col] >> 1;
        }
    }

};

Game Of Life

Ronald — Thu, 21 May 2020 02:11:49 +0000

let gameOfLife = function(board) {

    if (!board) return [];

    let copy = [],
        LIVE = 1,
        DEAD = 0,
        maxRow = board.length - 1,
        maxCol = board[0].length - 1;

    function getAdjacentCount(row, col, valueToCompare) {
        let sum = 0;
        for (let i = Math.max(row - 1, 0); i <= Math.min(row + 1, maxRow); i++) {
            for (let j = Math.max(col - 1, 0); j <= Math.min(col + 1, maxCol); j++) {
                if (i === row && j === col) continue;
                if (copy[i] && copy[i][j] !== undefined) {
                    if (copy[i][j] === valueToCompare) sum = sum + 1; //?
                }
                else {
                    if (board[i][j] === valueToCompare) sum = sum + 1; //?
                }
            }
        }
        return sum;
    }

    function getNextValue(row, col) {
        const val = board[row][col];
        let liveNeighbors = getAdjacentCount(row, col, LIVE);
        if (val === LIVE) {

            // Any live cell with fewer than two live neighbors dies, as if caused by under-population.
            if (liveNeighbors < 2) {
                return DEAD;
            }
            // Any live cell with more than three live neighbors dies, as if by over-population..
            else if (liveNeighbors > 3) {
                return DEAD;
            }
            // Any live cell with two or three live neighbors lives on to the next generation.
            return LIVE;
        }
        // cell is DEAD
        else {
            // Any dead cell with exactly three live neighbors becomes a live cell, as if by reproduction.
            if (liveNeighbors === 3) {
                return LIVE;
            }
            // no condition
            return DEAD;
        }
    }

    for (let row = 0; row <= maxRow; row++) {
        copy[row] = [];
        for (let col = 0; col <= maxCol;col++) {
            copy[row][col] = board[row][col];
            board[row][col] = getNextValue(row, col);
        }
    }

};

Array Plus One

Ronald — Wed, 20 May 2020 17:34:14 +0000

let plusOne = function(digits) {

    let carry = 1;
    for (let i = digits.length - 1; i >= 0; i--) {
        let sum = digits[i] + carry;
        if (sum >= 10) {
            digits[i] = 0;
            carry = 1;
        }
        else {
            digits[i] = sum;
            carry = 0;
        }
    }

    if (carry === 1) digits.unshift(carry);

    return digits;
};

LinkedList Palindrome

Ronald — Wed, 20 May 2020 17:20:07 +0000

let isPalindrome = function(head) {

    let slow = head, fast = head, val = [slow.val];

    while (fast.next) {
        if (fast.next.next) {
            fast = fast.next.next;
            slow = slow.next;
            val.push(slow.val);
        }
        else {
            fast = fast.next;
            slow = slow.next;
        }
    }

    while (slow) {
        if (slow.val !== val.pop()) {
            return false;
        }
        slow = slow.next;
    }

    return val.length === 0;
};

JS Algorithm Course

Ronald — Wed, 20 May 2020 15:18:06 +0000

httpss://www.youtube.com/watch?v=JgWm6sQwS_I

Happy Number

Ronald — Wed, 20 May 2020 12:41:18 +0000

let isHappy = function(n) {
    let visited = {};

    function sumOfSquare(num) {
        if (visited[num]) return false;
        visited[num] = true;

        let sum = 0;
        while (num > 0) {
            let d = num % 10; //?
            num = Math.floor(num / 10); //?
            sum += d * d;
        }

        if (sum === 1) {
            return true;
        }
        else {
            return sumOfSquare(sum);
        }
    }
    
    return sumOfSquare(n);
};

MaxStack

Ronald — Wed, 20 May 2020 03:15:12 +0000

class MaxStack {
    constructor() {
        this.results = [];
        this.sorted = [];
    }

    pop() {
        const val = this.results.pop();
        this.sorted.splice(this.sorted.lastIndexOf(val), 1);
        return val;
    }

    push(x) {
        this.results.push(x);
        this.sorted = [...this.results].sort((x, y) => x - y);
    }

    top() {
        return this.results[this.results.length - 1];
    }

    popMax() {
        const val = this.sorted.pop();
        this.results.splice(this.results.lastIndexOf(val), 1);
        return val;
    }

    peekMax() {
        return this.sorted[this.sorted.length - 1];
    }

}

MinStack

Ronald — Wed, 20 May 2020 03:03:29 +0000

class MinStack {
    constructor() {
        this.result = [];
        this.min = Number.MAX_SAFE_INTEGER;
    }

    push(x) {
        this.result.push(x)
        this.min = Math.min(x, this.min);
    };

    pop() {
        let val = this.result.pop()
        if (val === this.min) {
            this.min = Math.min(...this.result);
        }
    };

    top() {
        return this.result[this.result.length - 1];
    };

    getMin() {
        return this.min;
    };
}