200909-binary-gap.sh

#!/bin/bash
## binary-gap
## - returns length of binary gap in a integer
## version 0.0.1 - initial
##################################################
## problem:
## - find the length of longest contiguous string
##   of 0s between 1 or more 1s in the binary
##   representation of a positive integer
##################################################
## algorithm:
## 1. convert positive integer into binary string
## 1. trim leading and ending zeros from string
## 1. split string into list of gaps using
##    delimiter '1'
## 1. return length of longest gap
##################################################
hex2binary() { { local hex ; hex="${1}" ; }
  for i in $( seq ${#hex} )
  do
   case ${hex:$(( ${i} - 1 )):1} in
    0) bin='0000' ;;
    1) bin='0001' ;;
    2) bin='0010' ;;
    3) bin='0011' ;;
    4) bin='0100' ;;
    5) bin='0101' ;;
    6) bin='0110' ;;
    7) bin='0111' ;;
    8) bin='1000' ;;
    9) bin='1001' ;;
    a) bin='1010' ;;
    b) bin='1011' ;;
    c) bin='1100' ;;
    d) bin='1101' ;;
    e) bin='1110' ;;
    f) bin='1111' ;;
   esac
   echo -n "${bin}"
  done
}
dec2hex() { { local -i dec ; dec="${1}" ; }
  printf '%x\n' ${n}
}
trim() { { local bin ; bin="${1}" ; }
  echo "${bin}" | sed -e 's/^0*//' -e 's/0*$//' -e 's/^1*//' -e 's/1*$//'
}
if-debug() {
  test ! ${DEBUG:-false} = "true"
}
binary-gap() { { local -i n ; n="${1}" ; }
  if-debug || {
    echo -e "dec: \t\t${n}"
    echo -e "hex: \t\t$( dec2hex ${n} )"
    echo -e "bin: \t\t$( hex2binary $( dec2hex ${n} ) )"
    echo -e "bin(trimmed): \t$( trim $( hex2binary $( dec2hex ${n} ) ) )"
  } 1>&2
  local bin
  local bin_trim
  local gap
  bin=$( hex2binary $( dec2hex ${n} ) )
  bin_trim=$( trim ${bin} )
  gap=$(
    IFS='1'
    for b in ${bin_trim}
    do
     test ! "${b}" = '' || continue
     echo ${b}
    done | sort | tail -1
  )
  if-debug || {
    test ! "${gap}" || {
      echo -ne "bin(match):\t"
      echo "${bin}" | grep -e "${gap}" --color=auto
    }
  } 1>&2
  echo "${#gap}"
}
##################################################
if [ ${#} -eq 1 ]
then
 true
else
 exit 1 # wrong args
fi
##################################################
binary-gap ${@}
##################################################
## generated by create-stub2.sh v0.1.2
## on 9 Sep 2020
## see <https://github.com/temptemp3/sh2>
##################################################