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Input: binary string

Output: binary string that represents the binary input + 1

Example: Given 10111 as an input, output 11000

Limitations: Can't use arithmetic operators or functions (like + - * /)

Criterion: code-golf, the shortest code wins the big imaginary award.

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  • \$\begingroup\$ Related \$\endgroup\$ Commented Dec 17, 2020 at 15:04
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    \$\begingroup\$ Welcome to Code Golf! To be valid, a challenge needs to have a winning criterion. This is usually code-golf, but some other ones are commonly used as well. Another problem is that Do X without Y is often problematic. \$\endgroup\$ Commented Dec 17, 2020 at 15:08
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    \$\begingroup\$ Also, please use the Sandbox next time before posting a challenge, to get feedback on it. \$\endgroup\$ Commented Dec 17, 2020 at 15:13
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    \$\begingroup\$ Can you clarify what counts as arithmetic operators, and what input/output methods you would allow? \$\endgroup\$ Commented Dec 17, 2020 at 15:21
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    \$\begingroup\$ I assumed arithmetic operators are the usual gang of four + - * / and possibly ^ % (power and modulus) You should perhaps specify if 001 should result in 010 or if 10 is also ok. \$\endgroup\$ Commented Dec 17, 2020 at 15:46

2 Answers 2

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Perl 5, 38 bytes

s/0$/1/||s/0?(1+)$/1 .(0 x length$1)/e

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Basically: If(last digit is zero){ change it to 1} else {change the last consecutive 1's (with possibly a 0 ahead of them) with a 1 and a count of zeros that is the same number as the number of 1's matched at the end of the line.

Example input lines: 00000 00001 00111 1000 1011 111 1

Example output lines: 00001 00010 01000 1001 1100 1000 10

Perl 5, 37 bytes

Or one less byte with this if it's ok to not preserve leading 0's (i.e. 0001 → 10)

printf"%b\n",length 1 .(1x oct"0b$_")

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GNU sed <4.3, 49 46 44 34 30 bytes

s/.*/0&M/ # prepend 0 and append mark
: # label
s/0M/1/ # 0 incremented is 1
s/1M/M0/ # 1 incremented is 0 and the one to the left is incremented
t # if anything just changed, repeat until it doesn't (the M has disappeared)

(comments and all whitespace other that newlines are just for explanation)

This takes any amount of newline-separated binary numbers and increments each, it might give a number with leading 0s.

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  • \$\begingroup\$ Some parts of the question, such as whether there are negative numbers, were unspecified. Sed has no arithmetic, so this is guaranteed to not use them. \$\endgroup\$ Commented Dec 17, 2020 at 15:23
  • \$\begingroup\$ Doesn't work for repunits. \$\endgroup\$ Commented Dec 17, 2020 at 15:26
  • \$\begingroup\$ @Neil fixed, but the question doesn't specify what to do on overflow, such as whether 11111111 is -1. \$\endgroup\$ Commented Dec 17, 2020 at 15:29

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