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#!/usr/bin/env lua
--[[
Challenge 120
TASK #1 - Swap Odd/Even bits
Submitted by: Mohammad S Anwar
You are given a positive integer $N less than or equal to 255.
Write a script to swap the odd positioned bit with even positioned bit and
print the decimal equivalent of the new binary representation.
Example
Input: $N = 101
Output: 154
Binary representation of the given number is 01 10 01 01.
The new binary representation after the odd/even swap is 10 01 10 10.
The decimal equivalent of 10011010 is 154.
Input: $N = 18
Output: 33
Binary representation of the given number is 00 01 00 10.
The new binary representation after the odd/even swap is 00 10 00 01.
The decimal equivalent of 100001 is 33.
--]]
function swap_bits(n)
local result = 0
local bits = 1
while n > 0 do
if n % 2 ~= 0 then result = result + 2*bits end
n = math.floor(n / 2)
if n % 2 ~= 0 then result = result + 1*bits end
n = math.floor(n / 2)
bits = bits*4
end
return result
end
n = tonumber(arg[1])
n = swap_bits(n)
io.write(n, "\n")
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