#!/usr/bin/env ruby
#Programming Challenges 2003
#isbn: 0-387-00163-8
require "pp"
#1.6.1 the 3n+1 problem
def cycle_length(number,count=0)
    #number==1 is the defined end case
    return count+1 if number==1
    # if even divid else *3+1
    return number%2 == 0 ? cycle_length(number/2,count+1) : cycle_length((number*3)+1,count+1)
end
def n3plus1(min,max)
    raise "min must be less then max" if max<min
    max_cycles = (min..max).collect{|number| cycle_length(number)}.sort.last
    puts "#{min} #{max} #{max_cycles}"
end

#1.6.2  minesweeper

def get_chart(grid)
    lines = grid.split("\n")
    lines = lines.collect{|line| line.split("")}
    lines.each_index{|y|
        lines[y].each_index{|x|
            if lines[y][x].to_s=="*"
                [-1,0,1].each{|line|
                    [-1,0,1].each{|col|
                        next if (line==0 && col==0) || (line+y<0 || line+y>=lines.size) || (col+x<0 || col+y>=lines[y].size)
                       lines[y+line][x+col] = lines[y+line][x+col].to_i+1
                    } 
                }
            end    
        }
    }
    return lines
end

def minesweper
 boards = "4 4\n*...\n....\n.*..\n....".split(/\d\s\d\s/).reject!{|x| x.empty?}
 count = 1
 boards.each{|board|
    puts "Field ##{count}"
    puts get_chart(board).collect{|x| x.join("")}.join("\n").gsub(".","0")
    puts ""
    count+=1
 }
end

#1.6.3

def money_exchange
    input =<<-BILL
3
10
20
30
4
15
15.01
3
3.01
0
BILL
    input = input.split
loop{
    count = input.shift.to_i
    break if count==0
    values = input[0...count]
    input = input[count..-1]
    avg = 0.0
    values.each{|number| avg+= number.to_f}
    avg=avg/count
    change = 0.0
    values.select{|number| number.to_f<avg}.each{|number| change+=(avg-number.to_f)}
    puts "$"+change.to_s
}
end
money_exchange