// One-dimensional
const movies = [
  "Star Wars",
  "The Lord of the Rings",
  "Harry Potter",
  "The Matrix",
  "Dune",
];

console.log(movies[3]);

// Two-dimensional
const matrix = [
  [1, 2, 3],
  [4, 5, 6]
];

console.log(matrix[1][1]);

// Multidimensional
const  terrains = [
  ['desert', 'desert', 'grass', 'grass'],
  ['desert', 'grass', 'water', 'grass'],
  ['grass', 'grass', 'water', 'water'],
  ['grass', 'grass', 'grass', 'grass']
];

console.log(terrains[1][0]);

// Stack class
class Stack {

    // Array is used to implement stack
    constructor() {
        this.items = [];
    }

	// push method
    push(element) {
        // push element into the items
        this.items.push(element);
    }

    // pop method
    pop() {
        // return top most element in the stack
        // and removes it from the stack
        // Underflow if stack is empty
        if (this.items.length == 0)
            return "Underflow";
        return this.items.pop();
    }

    // peek method
    peek() {
        // return the top most element from the stack
        // but does'nt delete it.
        return this.items[this.items.length - 1];
    }

    // isEmpty method
    isEmpty() {
        // return true if stack is empty
        return this.items.length == 0;
    }

    // printStack method
    printStack() {
        var str = "";
        for (var i = 0; i < this.items.length; i++)
            str += this.items[i] + " ";
        return str;
    }

}

const stack = new Stack();

// Adding element to the stack
stack.push(10);
stack.push(20);
stack.push(30);

// Printing the stack element
// prints [10, 20, 30]
console.log(stack.printStack());

// returns 30
console.log(stack.peek());

// returns 30 and remove it from stack
console.log(stack.pop());

// returns [10, 20]
console.log(stack.printStack());

// Queue class
class Queue {
    // Array is used to implement a Queue
    constructor() {
        this.items = [];
    }

    // Functions to be implemented
    // enqueue method
    enqueue(element) {
        // adding element to the queue
        this.items.push(element);
    }

    // dequeue method
    dequeue() {
        // removing element from the queue
        // returns underflow when called
        // on empty queue
        if (this.isEmpty())
            return "Underflow";
        return this.items.shift();
    }

    // front method
    front() {
        // returns the Front element of
        // the queue without removing it.
        if (this.isEmpty())
            return "No elements in Queue";
        return this.items[0];
    }

    // isEmpty method
    isEmpty() {
        // return true if the queue is empty.
        return this.items.length == 0;
    }
    // printQueue method
    printQueue() {
        var str = "";
        for (var i = 0; i < this.items.length; i++)
            str += this.items[i] + " ";
        return str;
    }
}

// creating object for queue class
const queue = new Queue();
			

// Testing dequeue and pop on an empty queue
// returns Underflow
console.log(queue.dequeue());

// returns true
console.log(queue.isEmpty());

// Adding elements to the queue
// queue contains [10, 20, 30, 40, 50]
queue.enqueue(10);
queue.enqueue(20);
queue.enqueue(30);
queue.enqueue(40);
queue.enqueue(50);
queue.enqueue(60);

// returns 10
console.log(queue.front());

// removes 10 from the queue
// queue contains [20, 30, 40, 50, 60]
console.log(queue.dequeue());

// returns 20
console.log(queue.front());

// removes 20
// queue contains [30, 40, 50, 60]
console.log(queue.dequeue());

// printing the elements of the queue
// prints [30, 40, 50, 60]
console.log(queue.printQueue());

class Node {
    constructor(value, next) {
        this.value = value;
        this.next = null;
    }
}

class List {
    constructor() {
        this.head = null;
        this.tail = null;
    }

    getNode(index) {
        if (index < 0) return 0;
        if (index === 0 && this.head) return this.head;

        let currentNode = this.head;
        while (index > 0 && currentNode && currentNode.next) {
            currentNode = currentNode.next;
            index--;
        }

        if (index !== 0) {
            return null;
        }
        return currentNode;
    }

    get(index) {
        return this.getNode(index).value;
    }

    push(value) {
        if (!this.head) {
            this.head = new Node(value);
            this.tail = this.head;
            return this;
        }

        this.tail.next = new Node(value);
        this.tail = this.tail.next;

        return this;
    }

    pop() {
        if (!this.head) {
            return null;
        }

        if (!this.head.next) {
            const temp = this.head.value;
            this.head = this.tail = null;
            return temp;
        }

        let currentNode = this.head;

        while (currentNode.next.next !== null) {
            currentNode = currentNode.next;
        }

        const temp = this.tail.value;
        this.tail = currentNode;
        currentNode.next = null;

        return temp;
    }

    remove(index) {
        const prev = this.getNode(index - 1);
        const current = this.getNode(index);

        if (prev && current && current.next) {
            prev.next = current.next;
        } else if (!prev && current) {
            this.head = current.next;
        }

        return current;
    }

    shift() {
        if (this.head) {
            const temp = this.head.value;
            if (this.head.next === null) {
                this.tail = null;
            }
            this.head = this.head.next;
            return temp;
        }

        return null;
    }

    unshift(value) {
        const newNode = new Node(value);
        newNode.next = this.head;
        this.head = newNode;
        return this;
    }

    toString() {
        let result = '';
        let current = this.head;
        while (current) {
            result += `${current.value}${current.next ? ', ' : ''}`;
            current = current.next;
        }
        return result;
    }
}

const list = new List();

list.push(1).push(2).push(3).push(4);

console.log(list.toString());

console.log(list.remove(1));
console.log(list.toString());
console.log(list.remove(0));
console.log(list.toString());
console.log(list.remove(333));
console.log(list.toString());

const WEIRD_NUMBER = 23;

function hash(str, limit = 53) {
    let result = 0;

    for(let i=0; i < Math.min(str.length, 100); i++) {
        result += (str.charCodeAt(i) - 96) * WEIRD_NUMBER;
    }

    return Math.abs(result % limit);
}


class HashTable {
    constructor() {
        this.array = new Array(10);
    }

    set(key, value) {
        const keyHash = hash(key, this.array.length);
        
        if(!this.array[keyHash]) {
            this.array[keyHash] = [];
        }
        const bucket = this.array[keyHash];
        bucket.push([key, value]);
    }

    get(key) {
        const keyHash = hash(key, this.array.length);
        const bucket = this.array[keyHash];

        for(let i = 0; i < bucket.length; i++) {
            const entries = bucket[i];
            if (entries[0] === key) {
                return entries[1];
            }
        }
            
        return;
    }

    keys() {
        const result = [];

        for (let i = 0; i < this.array.length; i++) {
            if(this.array[i]) {
                this.array[i].forEach(entry => {
                    result.push(entry[0]);
                });
            }
        }

        return result;
    }
}


const test = new HashTable();

test.set('black', '#000');
test.set('white', '#fff');
test.set('red', '#f00');
test.set('blue', '#00f');
test.set('green', '#0f0');

console.log(test);

console.log(test.get('green'));
console.log(test.get('black'));
console.log(test.get('red'));
console.log(test.get('white'));
console.log(test.keys());

const map1 = new Map();

map1.set('a', 1);
map1.set('b', 2);
map1.set('c', 3);

console.log(map1.get('a'));
// Expected output: 1

map1.set('a', 97);

console.log(map1.get('a'));
// Expected output: 97

console.log(map1.size);
// Expected output: 3

map1.delete('b');

console.log(map1.size);
// Expected output: 2

class Node {
	constructor(value) {
		this.value = value;
		this.left = null;
		this.right = null;
	}
}

class BinarySearchTree {
	constructor() {
		this.root = null;
	}
	// Add new Node with {value}
	add(value) {
		if(!this.root) {
			this.root = new Node(value);
			return this;
		}

		let temp = this.root;

		while(true) {
			if(temp.value < value) {
				if (!temp.right) {
					temp.right = new Node(value);
					return this;
				}

				temp = temp.right;
			} else {
				if(!temp.left) {
					temp.left = new Node(value);
					return this;
				}

				temp = temp.left;
			}
		}
	}

	// Find Node with {value}
	find(value) {
		let temp = this.root;

		if(!temp) {
			return null;
		}

		while(true) {
			if(temp.value === value) {
				return temp;
			} else if (temp.value < value) {
				if(!temp.right) {
					return null;
				} 
				temp = temp.right;
			} else {
				if (!temp.left) {
					return null;
				}
				temp = temp.left;
			}
		}
	}

	// Check if Node with {value} exists
	contains(value) {
		let node = this.find(value);
		if (node) {
			return true;
		}
		return false;
	}

	// Traversing
	//    B
	// A     C
	
	// A, B, C
	traverseInOrder(node = this.root) {
	   let res = []; 
	   function traverse(node) {
			if (node.left) {
				traverse(node.left)
			} 

			res.push(node.value)

			if (node.right) {
				traverse(node.right)
			}
	   }

	   traverse(node);

	   return res;
	}

	// B, A, C
	traversePreorder(node = this.root) {
		return node
		? [node.value, ...this.traversePreorder(node.left), ...this.traversePreorder(node.right)]
		: [];        
	}

	// A, C, B
	traversePostorder() {
		let res = []; 
		function traverse(node) {
			 if (node.left) {
				 traverse(node.left)
			 } 
 			 
			 if (node.right) {
				 traverse(node.right)
			}

			res.push(node.value)
		}
 
		traverse(this.root);
 
		return res;
	}
}

const tree = new BinarySearchTree();
tree.add(5).add(2).add(-1).add(6).add(100);

// console.log(tree);

//    5
//  2    6
//         100

console.log(tree.find(2));
console.log(tree.find(100));
console.log(tree.find(1000000));
console.log(tree.contains(2));
console.log(tree.contains(17));

console.log('Preorder  ', tree.traversePreorder());
console.log('Inorder ', tree.traverseInOrder());
console.log('Postorder ', tree.traversePostorder());

function Heap(data = []) {
	this.data = data;
	this.size = data.length;

	if (data.length > 1) {
		this.buildMaxHeap();
	}
}

Heap.prototype = {
	swap: function(i, j) {
		let temp = this.data[i];
		this.data[i] = this.data[j];
		this.data[j] = temp;
	},

	maxHeapify: function(i) {
		let leftIdx = 2*i + 1;
		let rightIdx = 2*i + 2;
		let largest = i;

		if ( leftIdx < this.size && this.data[leftIdx] > this.data[largest]) {
			largest = leftIdx;
		}

		if (rightIdx < this.size && this.data[rightIdx] > this.data[largest]) {
			largest = rightIdx;
		}

		if (largest !== i) {
			this.swap(largest, i);
			this.maxHeapify(largest);
		}
	},

	buildMaxHeap: function() {
		for(let i = Math.floor(this.size / 2); i >= 0; i--) {
			this.maxHeapify(i);
		}
	},

	bubbleUp: function() { 
		let curIdx = this.size - 1;	

		while(curIdx > 0) { // O(log(n)) as we deviding parent index by 2 every iteration
			let parentIdx = Math.floor((curIdx - 1)/ 2);
			let lastVal = this.data[curIdx];	
			let parentData = this.data[parentIdx];
			
			if (parentData >= lastVal) { return; }
			else {
				this.data[parentIdx] = lastVal;
				this.data[curIdx] = parentData;
				curIdx = parentIdx;
			}
		}
	},

	push: function(val) {
		this.data.push(val);
		this.size++;
		this.bubbleUp();
	},

	decrementSize: function() { this.size--; },

	print: function() { console.log(this.data) }
}



const heap = new Heap();

heap.push(20);
heap.push(10);
heap.push(30);
heap.push(1);
heap.push(100);

heap.print();

/*
Output: 
[ 100, 30, 20, 1, 10 ]

The tree looks like:

   100
   / \
  30 20
 / \
1  10

*/

class PriorityQueue {
    constructor(){
      this.values = [];
    }
    enqueue(val, priority) {
      this.values.push({val, priority });
      this.sort();
    }
    dequeue() {
      return this.values.shift();
    }
    sort() {
      this.values.sort((a, b) => a.priority - b.priority);
    };
  }


  
class WeightedGraph {

    /**
     *  In graph theory and computer science, an adjacency list is a collection of unordered lists used to represent a finite graph
     */
    constructor() {
        this.adjacencyList = {};
    }

    /**
     * "Vertex" is a synonym for a node of a graph, i.e., one of the points on which the graph is defined and which may be connected by graph edges. 
     *  
     * Time complexity: O(1)
     */
    addVertex(vertex) {
        if(this.adjacencyList[vertex]) {
            console.warn(`"${vertex}" vertex already present into adjacency list. Overriding ${vertex} `);
        }

        this.adjacencyList[vertex] = [];
    }

    /**
     * For an undirected graph, an unordered pair of nodes that specify a line joining these two nodes are said to form an edge.
     * 
     * Time complexity: O(1)
     */
    addEdge(vertex1, vertex2, weight) {
        if(!this.adjacencyList[vertex1]) {
            console.info(`Creating vertex "${vertex1}"`)
            this.addVertex(vertex1);
        }

        if(!this.adjacencyList[vertex2]) {
            console.info(`Creating vertex "${vertex2}"`)
            this.addVertex(vertex2);
        }

        this.adjacencyList[vertex1].push({ node: vertex2, weight });
        this.adjacencyList[vertex2].push({ node: vertex1, weight });
    }

    // O(|E|)
    removeEdge(vertex1, vertex2) {
        this.adjacencyList[vertex1] = this.adjacencyList[vertex1].filter(val => val !== vertex2);
        this.adjacencyList[vertex2] = this.adjacencyList[vertex2].filter(val => val !== vertex1);
    }

    // O(|V| + |E|)
    removeVertex(vertex) {
        this.adjacencyList[vertex]
            .forEach(vertex2 => this.removeEdge(vertex, vertex2));

        delete this.adjacencyList[vertex];
    }

    /**
     * Breadth-first search (BFS) is an algorithm for traversing or searching tree or graph data structures. 
     * It starts at the tree root and explores all of the neighbor nodes at the present depth prior to moving on to the nodes at the next depth level.
     */
    breadthFirstSearch() {
        const res = [];
        const keys = Object.keys(this.adjacencyList);
        const queue = [keys[0]];
        const visited = { [keys[0]]: true };

        while(queue.length) {
            const node = queue.shift();
            res.push(node);
            this.adjacencyList[node].forEach(vrt => {
                if(!visited[vrt.node]) {
                    visited[vrt.node] = true;
                    queue.push(vrt.node);
                } 
            });
        }

        return res;
    }

    /**
     * Depth-first search (DFS) is an algorithm for traversing or searching tree or graph data structures.
     * The algorithm starts at the root node (selecting some arbitrary node as the root node in the case of a graph)
     * and explores as far as possible along each branch before backtracking.
     */
    depthFirstSearch() {
        const res = [];
        const keys = Object.keys(this.adjacencyList);
        const visited = {};

        const traverse = node => {
            if (!visited[node]) {
                visited[node] = true;
                res.push(node);
                this.adjacencyList[node].forEach(vrt => traverse(vrt.node))
            } 
        }

        traverse(keys[0]);

        return res;
    }

    /**
     * 
     * Dijkstra's algorithm (or Dijkstra's Shortest Path First algorithm, SPF algorithm)[1] is an algorithm for finding the shortest paths
     * between nodes in a graph, which may represent, for example, road networks. 
     * 
     * It was conceived by computer scientist Edsger W. Dijkstra in 1956 and published three years later.
     */
    dijkstra(vertex1, vertex2) {
        const previous = {};
        const dist = {};
        const keys = Object.keys(this.adjacencyList);
        const priorityQueue = new PriorityQueue();
        let smallest;

        // init
        keys.forEach(key => {
            if (key === vertex1) {
                dist[key] = 0;
                priorityQueue.enqueue(key, 0);
            } else {
                dist[key] = Infinity;
                priorityQueue.enqueue(key, Infinity);
            } 
            previous[key] = null;
        });

        // take smallest dist vertex
        while(priorityQueue.values.length) {
            smallest = priorityQueue.dequeue().val;

            if(smallest === vertex2) {
                // wohoo
                const res = [];
                let curr = previous[vertex2]
                while(curr) {
                    res.push(curr);
                    curr = previous[curr];
                }

                return res.reverse().concat(vertex2);
            } 

            this.adjacencyList[smallest].forEach(el => {
                // calc dist to neighbour node
                let candidate = el.weight + dist[smallest];
                if (dist[el.node] > candidate) {
                    dist[el.node] = candidate;
                    previous[el.node] = smallest;
                    priorityQueue.enqueue(el.node, candidate)
                }
            })
        }


    }

}

/**
*  Example:
*         
*         7
*      C --- D
*   1 /   3   \ 2
*    A ------- B
*  3 |    2    | 5
*    F ------- K
*  4 \    1   / 1
*     J ---- I
* 
*/   

const graph = new WeightedGraph();

graph.addVertex('A');
graph.addVertex('B');
graph.addVertex('C');
graph.addVertex('D');
graph.addVertex('F');
graph.addVertex('K');
graph.addVertex('J');
graph.addVertex('I');

graph.addEdge('C', 'D', 7);
graph.addEdge('A', 'B', 3);
graph.addEdge('F', 'K', 2);
graph.addEdge('J', 'I', 1);

graph.addEdge('C', 'A', 1);
graph.addEdge('A', 'F', 3);
graph.addEdge('F', 'J', 4);
graph.addEdge('D', 'B', 2);
graph.addEdge('B', 'K', 5);
graph.addEdge('K', 'I', 1);

console.log(graph.breadthFirstSearch());
console.log(graph.depthFirstSearch());
console.log('A->D', graph.dijkstra('A', 'D'));
console.log('A->K', graph.dijkstra('A', 'K'));
console.log('A->I', graph.dijkstra('A', 'I'));

const movies = [
  'LoTR',
  'Back to the Future',
];

// .push() - add a new element
values.push('Star Wars', 'Matrix');

// .pop() - remove the last one
values.pop();

// .reverse() - reverse an array
values.reverse();

// .unshift() // add a new elemnt
// to the beginning of an array
values.unshift('Avatar');

// .sort()
values.sort();

// .filter()
values.filter();