Teaching Sample

Problem Description

Write a function twins that takes a string as input, and returns a copy of the string where every character is repeated twice

Input: "abc"
Output: "aabbcc"

Input: "a"
Output: "aa"

Input: ""
Output: ""

Sample Solution in Action

def twins(input):
  output = ''
  for elem in input:
    output = output + elem + elem
  return output

'abc'

Sample Solution in Action

def twins(input):
  output = ''
  for elem in input:
    output = output + elem + elem
  return output

'abc'

output:''

Sample Solution in Action

def twins(input):
  output = ''
  for elem in input:
    output = output + elem + elem
  return output

'abc'

output:''

elem

Sample Solution in Action

def twins(input):
  output = ''
  for elem in input:
    output = output + elem + elem
  return output

'abc'

output:'aa'

elem

Sample Solution in Action

def twins(input):
  output = ''
  for elem in input:
    output = output + elem + elem
  return output

'abc'

output:'aa'

elem

Sample Solution in Action

def twins(input):
  output = ''
  for elem in input:
    output = output + elem + elem
  return output

'abc'

output:'aabb'

elem

Sample Solution in Action

def twins(input):
  output = ''
  for elem in input:
    output = output + elem + elem
  return output

'abc'

output:'aabb'

elem

Sample Solution in Action

def twins(input):
  output = ''
  for elem in input:
    output = output + elem + elem
  return output

'abc'

output:'aabbcc'

elem

Sample Solution in Action

def twins(input):
  output = ''
  for elem in input:
    output = output + elem + elem
  return output

'abc'

output:'aabbcc'

What went wrong?

def twins(input):
  output = ''
  for elem in input:
    output = elem + elem
  return output

'abc'

What went wrong?

def twins(input):
  output = ''
  for elem in input:
    output = elem + elem
  return output

'abc'

output:''

What went wrong?

def twins(input):
  output = ''
  for elem in input:
    output = elem + elem
  return output

'abc'

output:''

elem

What went wrong?

def twins(input):
  output = ''
  for elem in input:
    output = elem + elem
  return output

'abc'

output:'aa'

elem

What went wrong?

def twins(input):
  output = ''
  for elem in input:
    output = elem + elem
  return output

'abc'

output:'aa'

elem

What went wrong?

def twins(input):
  output = ''
  for elem in input:
    output = elem + elem
  return output

'abc'

output:'bb'

elem