snake.rb

# Given a square matrix of integer numbers, write a function that prints the
# matrix to the standard output(stdout) on a single line starting in the
# upper-left corner and continuing clockwise, in circles, from the exterior
# towards interior.
# 
# Note that your function will receive the following arguments:
# - matrix: which is an array of integers giving the matrix as follows. The
#   first width elements in the array represent the first line of the matrix,
#   the next width elements represent the second line of the matrix and so on.
# - width: which is an integer value giving the width of the square matrix 
# 
# Data contraints
# The width values will not exceed 250
# All elements in the matrix are integer numbers in the following rnage[1, 2^31-1]
# 
# Efficiency contraints
# Your function is expected to print the result in less than 2 seconds
# 
# Example
# Input: matrix = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16], width = 4
# Output: [1 2 3 4 8 12 16 15 14 13 9 5 6 7 11 10]
# 
# Explanation
# 1 2 3 4
# 5 6 7 8
# 9 10 11 12
# 13 14 15 16

RIGHT = 1
DOWN = 4
LEFT = -1
UP = -4

def roll_snake(matrix, width)
    # Write your code here
    # To print results to the standard output you can use puts
    # Example puts "Hello world!"

    visited = Array.new

    direction = RIGHT
    pos = 0
    count = 0

    while true
    	turned = false
    	visited << matrix[pos]
    	
    	if (count >= width -1 || 
    				visited.include?(matrix[pos+direction])) && 
    				direction == RIGHT
    		count = 0
    		direction = DOWN
    		turned = true
    	end
    	if (count >= width -1 || 
    				visited.include?(matrix[pos+direction])) && 
    				direction == DOWN
    		count = 0
    		direction = LEFT
    		turned = true
    	end
    	if (count >= width || 
    				visited.include?(matrix[pos+direction])) && 
    				direction == LEFT
    		count = 0
    		direction = UP
    		turned = true
    	end
    	if (count >= width || 
    				visited.include?(matrix[pos+direction])) && 
    				direction == UP
    		count = 0
    		direction = RIGHT
    		turned = true
    	end
    	if turned = true && visited.include?(matrix[pos+direction])
    		break
    	end
    	count += 1
    	pos += direction
    end
    print visited.join(" ")
end

roll_snake([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16], 4)