Remove White Spaces

Coding Skill Exercise #23

Remove White Spaces

Write a method to remove white spaces from a given string. The string may contain tabs or spaces.

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title: Remove Whitespaces excerpt: Solution for a common string interview question. tags: two-pointers-moving-in-same-direction read-and-write-pointers two-pointers-left-to-right-scan

The string is modified by copying only non white spaces characters. Read pointer skips any white space or tab characters, it is copied to the string to the location pointed by write pointer. The substring formed from the index 0 to the write index gives the string without white spaces.

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def remove_white_spaces(s)
  if (!s || s.size == 0)
    return
  end
  
  read = 0
  write = 0
  
  while read < s.size
    if s[read] != ' ' && s[read] != '\t'
      s[write] = s[read]
      write += 1
    end
    read += 1
  end
  
  s[0, write]
end

s = '     All greek  to    me.    '

p remove_white_spaces(s)

Building Blocks

• Read and Write Pointers
• Two Pointers Moving in Same Direction

The read and write pointers are initialized to 0 and move from left to right in the input string.