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Spiral Jetty

The Question

Write a function that will generate a spiral

of the form below:

resultArray = [[0,0],[1,0],[1,1],[0,1],[-1,1],[-1,0],...,[-2,-1],[-2,-2]]

        var spiral = function(n){

            var direction;
            x=0;
            y=0;
            resultArray = [[0,0]]
            for (var k=1; k < n; k++){
                direction = k%2;
                if (direction === 1){
                   // Move to the right then move up
                }
                if (direction === 0){
                   // Move to the left then move down
                }
            }
            return resultArray;
        }

k = 1 : [[0,0],[1,0],[1,1]]

k = 2 : [[0,0],[1,0],[1,1], ]

[0,1],[-1,1],[-1,0],[-1,-1]

k=1

k=2

Approach

- for each k, you take

k steps in both the x

and y direction

- alternate between

+ and - direction

            for (var k=1; k < n; k++){
                direction = k%2;
                if (direction === 1){
                    var i = 0;
                    var j = 0;
                    while(i < k){
                        x++;
                        resultArray.push([x,y]);
                        i++
                    }
                    while(j < k){
                        y++;
                        resultArray.push([x,y])
                        j++
                    }
                }
                if (direction === 0){
                    var i = 0;
                    var j = 0;
                    while (i < k){
                        x--;
                        resultArray.push([x,y]);
                        i++;
                    }
                    while (j < k){
                        y--;
                        resultArray.push([x,y]);
                        j++
                    }
                }
            }

- x and y represent

the coordinates

- i and j control the

number of steps taken

i = 0

i = 1

j = 0

j = 1

i = 1

i = 0

i = 2

Approach

Full Solution

repl.it

Another Solution

'use strict';

var spiral = function(maxLength){
    var xPos=0;
    var yPos=0;
    var resultArray = [[0,0]];
    
    //each large iteration creates an 'L' of the spiral
    for (let thisLength = 1; thisLength < maxLength; thisLength++){
        
        //control ++ or -- vertically and horizontally
        var goPositive = thisLength % 2; 

        //iterate horizontally left or right
        for (let xIterator = 0; xIterator < thisLength; xIterator++){
            goPositive ? xPos++ : xPos--;
            //push new coordinates
            resultArray.push([xPos,yPos])
        }

        //iterate vertically up or down
        for (let yIterator = 0; yIterator < thisLength; yIterator++){
            goPositive ? yPos++ : yPos--;
            //push new coordinates
            resultArray.push([xPos,yPos])
        }
    }
   return resultArray;
}

Another Solution

function tropicalSpiral(n) {
	let x = 0,
		y = 0,
		result = [[0, 0]],
		z = n * -1,
		k = 1;
	
	while (x !== z && y !== z) {
		// increment x positive
		for (let i = 0; i < k; i++) result.push([++x, y]);
		
		// increment y positive
		for (let j = 0; j < k; j++) result.push([x, ++y]);
		
		// increment our 'k' threshold
		k++;
		
		// decrement x negative
		for (let i = 0; i < k; i++) result.push([--x, y]);
		// decrement y negative
		for (let j = 0; j < k; j++) result.push([x, --y]);
	}
	return result;
}

tropicalSpiral(1);