Created
May 3, 2012 02:41
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Code kata two: karate chop
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# Mixin module for enhancing the Array class | |
module KarateChopArray | |
def left_side | |
slice(0, self.size/2) | |
end | |
def right_side | |
slice(self.size/2, self.size-1) | |
end | |
def in_left_side?(num) | |
num < middle_number | |
end | |
def in_right_side(num) | |
num > middle_number | |
end | |
def middle_number | |
self[middle_index] | |
end | |
def middle_index | |
size/2 | |
end | |
end | |
#include the mixin into the Array class | |
class Array | |
include KarateChopArray | |
end | |
def chop(n, arr) | |
return -1 unless arr.include?(n) | |
return 0 if arr.size == 1 | |
offset = 0 | |
chop_with_offset(n, arr, offset) | |
end | |
def chop_with_offset(n, arr, offset) | |
middle_number = arr.middle_number | |
if n == middle_number | |
#offset += arr.left_side.size | |
return arr.middle_index + offset | |
elsif arr.in_left_side?(n) | |
return chop_with_offset(n, arr.left_side, offset) | |
else | |
offset += arr.left_side.size | |
return chop_with_offset(n, arr.right_side, offset) | |
end | |
end |
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# | |
# inicio = 0 | |
# fin_idx = arr.size | |
#[ 0 1 2 3 4 5 6 7 8] | |
# | |
# assert_equal(0, chop(1, [1, 3, 5])) | |
# n = 1 | |
# start 0, end 2, mid = 1, mid_val 3, | |
# start 0, end 0 | |
# | |
#assert_equal(1, chop(3, [1, 3, 5])) | |
# n = 3, start=0, end=2, mid=1, mid_val=3 | |
# | |
#assert_equal(2, chop(5, [1, 3, 5, 7])) | |
# n = 5 | |
# start=0, end = 3, mid = 1, mid_val=3 | |
# start = 2, end=3 | |
def chop(n, arr) | |
#debugger | |
return -1 if arr.empty? | |
return 0 if arr.size == 1 && arr[0] == n | |
starting_idx = 0 | |
end_idx = arr.size - 1 | |
while end_idx > starting_idx | |
middle_idx = (end_idx + starting_idx)/2 | |
middle_value = arr[middle_idx] | |
return middle_idx if middle_value == n | |
if n < middle_value | |
end_idx = middle_idx - 1 | |
else | |
starting_idx = middle_idx + 1 | |
end | |
end | |
return end_idx if arr[end_idx] == n | |
return -1 # not found | |
end |
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