Remove character at specified index

Question

(heavily inspired by Element of string at specified index)

Given a string s and an integer n representing an index in s, output s with the character at the n-th position removed.

0-indexing and 1-indexing are allowed.

• For 0-indexing, n will be non-negative and less than the length of s.
• For 1-indexing, n will be positive and less than or equal to the length of s.

s will consist of printable ASCII characters only (\x20-\x7E, or   through ~).

Any reasonable input/output is permitted. Standard loopholes apply.

Testcases (0-indexed):

n s        output
0 "abcde"  "bcde"
1 "abcde"  "acde"
2 "a != b" "a = b"
3 "+-*/"   "+-*"
4 "1234.5" "12345"
3 "314151" "31451"

Testcases (1-indexed):

n s        output
1 "abcde"  "bcde"
2 "abcde"  "acde"
3 "a != b" "a = b"
4 "+-*/"   "+-*"
5 "1234.5" "12345"
4 "314151" "31451"

This is code-golf, so shortest answer in bytes wins.

Answer 1

C#, 20 19 bytes

s=>n=>s.Remove(n,1)

Answer 2

Alice, 13 12 bytes

Thanks to Leo for saving 1 byte.

/oI\!e]&
@ q

Try it online!

First line of the input is the string, second line is the 0-based index.

Explanation

/    Reflect to SE. Switch to Ordinal. While in Ordinal mode, the IP bounces
     diagonally up and down through the code.
I    Read the first line of input (the string).
!    Store the string on the tape, which writes the characters' code points to 
     consecutive cells (the tape is initialised to all -1s).
]    Move the tape head right. This moves it by an entire string, i.e. to the
     cell after the -1 that terminates the current string.
     The IP bounces off the bottom right corner and turns around.
]    Move the tape head right by another cell.
!    Store an implicit empty string on the tape, does nothing. It's actually
     important that we moved the tape head before this, because otherwise it
     would override the first input code point with a -1.
I    Read the second line of input (the index) as a string.
/    Reflect to W. Switch to Cardinal.
     The IP wraps around to the last column.
&]   Implicitly convert the first input to the integer value it contains
     (the index) and move the tape head that many cells to the right, i.e.
     onto the character we want to delete. Note that Ordinal and Cardinal mode
     have two independent tape heads on the same tape, so the Cardinal tape
     head is still on the first cell of the string input before we do this.
e!   Store a -1 in the cell we want to delete.
\    Reflect to SW. Switch to Ordinal.
q    Push the entire tape contents as a single string. This basically takes
     all cells which hold valid code points from left to right on the tape 
     and concatenates the corresponding characters into a single string. Since
     we wrote a -1 (which is not a valid code point) over the target character,
     this will simply push the entire input string without that character.
o    Output the result.
@    Terminate the program.

Answer 3

Japt, 2 bytes

jV

Try it online!

Answer 4

K (Kona), 1 byte

_

Gotta love builtins. 0-based indexing. Usage:

k)"abcdef" _ 3
"abcef"

Answer 5

Haskell, 28 24 Bytes

-4 byte thanks to Laikoni, this version is 1-indexed.

s#n=take(n-1)s++drop n s

Old answer:

f(s:t)0=t;f(s:t)n=s:f t(n-1)

A simple recursive function that takes the value, it's 0-indexed.

My first time code-golfing so maybe it's not the optimal solution. Oh well.

Answer 6

CJam, 4 bytes

q~Lt

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Explanation

q~    e# Read and eval input (push the string and number to the stack).
  Lt  e# Set the nth element of the string to the empty string.

Answer 7

V, 3 bytes

À|x

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This uses 1-indexing.

Answer 8

Mathematica, 18 bytes

1-indexed

#2~StringDrop~{#}&

input

[1, "abcde"]

thanks Martin Ender

Answer 9

MATL, 3 bytes

&)&

Uses 1-based indexing.

Try it online! Or verify all test cases.

Explanation

&    % Specify secondary default number of inputs/outputs for next function
)    % Implicitly input string and number. Index: with & it pushes the char
     % defined by the index and the rest of the string
&    % Specify secondary default number of inputs/outputs for next function
     % Implicitly display (XD): with & it only displays the top of the stack

In the modified version with all the test cases, the code is within an infinite loop `...T until no input is found. At the end of each iteration the display function (XD) is explicitly called, and the stack is cleared (x) to ready it for the next iteration.

Answer 10

Vim, 7 bytes

jDk@"|x

How it works:

It expects two lines; one with the string and one with the number.

1. Go to line two, copy the number into register
2. Go to first line and then go to column in the register with @"|
3. Delete the character under the cursor

Answer 11

Java 8, 39 bytes

s->n->s.substring(0,n)+s.substring(n+1)

Try it here.

Java 7, 67 bytes

String c(int n,String s){return s.substring(0,n)+s.substring(n+1);}

Try it here.

Answer 12

Ruby, 16 bytes

->n,s{s[n]='';s}

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Answer 13

GCC c function, 25

1-based indexing.

f(n,s){strcpy(s-1,s+=n);}

Plenty of undefined behavior here so watch out for stray velociraptors:

• The strcpy() man page says If copying takes place between objects that overlap, the behavior is undefined. Here there clearly is overlap of the src and dest strings, but it seems to work, so either glibc is more careful or I got lucky.
• The answer is reliant on the fact that the s+=n happens before the s-1. The c standard gives no such guarantees, and in fact calls this out as undefined behaviour. Again, it seems to work as required with the gcc compiler on x86_64 Linux.

Try it online.

Answer 14

Jelly, 3 bytes

Ṭœp

A full program taking the (1-based) index and the string (in that order) and printing the result.

As a dyadic function it returns a list of the two parts.

In fact the index may be a list of n indices, in which case it returns a list of the n-1 parts.

Try it online!, or see a test suite.

How?

Ṭœp - Main link: number i, string s                   e.g. "fish 'n chips", 6
Ṭ   - untruth - get a list with 1s at the indexes of i      000001 <-- i.e. [0,0,0,0,0,1]
 œp - partition s at truthy indexes without borders       ["fish ","n chips"]
    - implicit print                                        fish n chips

As an example of using multiple indexes:

      "fish and chips", [6,8]
Ṭ      00000101 <- i.e. [0,0,0,0,0,1,0,1]
 œp  ["fish ","n"," chips"] 
       fish n chips

Answer 15

Haskell, 15 bytes

This requires the recently released GHC 8.4.1 (or higher). Now <>, as a function on Semigroups, is in Prelude. It is particularly useful on the function Semigroup

take<>drop.succ

Try it online!
Since tio is using an older bersion of GHC, I've imported <> in the header.

Answer 16

R, 40 bytes

Just goes to show the variety of ways, none of which particularly compact, you can fiddle with strings in R.

function(s,n)intToUtf8(utf8ToInt(s)[-n])

Answer 17

05AB1E, 6 bytes

vNÊiy?

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Explanation

v       # for each element, index (y,N) in input1
 NÊi    # if N is not equal to input2
    y?  # print y

Answer 18

Pyth, 3 bytes

.DE

Try it here.

Takes index first.

Answer 19

JS (ES6), 41 32 31 bytes

y=>i=>y.slice(0,i++)+y.slice(i)

Based on this. Takes input through currying, first is string, second is index.

-9 thanks to @JohanKarlsson

-1 thanks to @ETHproductions

Answer 20

vim, 10 7

DgJ@"|x

Takes 1-indexed input in the following format:

2
abcde

D      delete the number on the first line into register "
gJ     remove the newline while preserving whitespace on line 2
@"     run the " register as a macro - input is used as a count for...
|      the "go to nth column" command
x      delete the character at the cursor

Thanks to @DJMcMayhem for 3 bytes!

Answer 21

brainfuck, 14 bytes

,[>,.<-],,[.,]

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Reads zero-based one-byte index immediately followed by the string.

Answer 22

Java 8, 45 41 bytes

s->n->new StringBuffer(s).deleteCharAt(n)

Saved 4 bytes thanks to @OlivierGrégoire

My first code golf answer in something other than C#, even if it isn't the shortest for Java yet.

Answer 23

APL (Dyalog), 5 bytes

Zero-indexed. Takes index n as left argument and string s as right argument.

↑,1↓↓

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↑ n characters from s

, followed by

1↓ one character dropped from

↓ n characters dropped from s

Answer 24

Python 3, 24 bytes

lambda n,a:a[:n]+a[n+1:]

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Answer 25

Jelly, 4 bytes

Jḟị³

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Explanation

Jḟị³
J    - all indices of the input string
 ḟ   - except for the input index
  ị  - return the elements at those indices
   ³ - of the input string

Answer 26

05AB1E, 5 bytes

ā²ÊÏJ

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ā     # push range(1, len(input string) + 1)
 ²Ê   # Check each for != to input index
   Ï  # Keep characters from input where this array is 1
    J # Join

Answer 27

PHP, 42 Bytes

0 indexed

<?=substr_replace($argv[1],"",$argv[2],1);

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Answer 28

Befunge-98, 35 27 25 bytes

-4 bytes thanks to @eush77

&#;1-:!#v_~,;
_@#:~;#~<;,

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1-indexed, note that the input has a trailing null-byte.

Answer 29

PHP, 41 bytes, 35 bytes excluding ?php

<?php $argv[1][$argv[2]]='';echo$argv[1];

0-indexed

TIO

Answer 30

Japt, 3 2 bytes

jV

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