Introduction

The Remove Spaces from String problem involves removing all space characters from a string.

Given a string s, the task is to:

  • remove all blank spaces
  • return the modified string

This problem helps in understanding:

  • string traversal
  • filtering techniques
  • character processing
  • text cleaning operations

Example

Input:s = "hello world"

Output:
"helloworld"

Explanation:
All spaces are removed from the string.

Input:
s = " c o d i n g "

Output:
"coding"

Explanation:
Only non-space characters are kept.

Constraints

 1 <= s.length <= 10^5s contains printable ASCII characters

Approach 1 : Brute Force (Built-in Method)

Explanation

The simplest way to solve this problem is:

  1. Use built-in replace function
  2. Replace spaces with empty string

This approach is easy and efficient.

Steps

  1. Take input string.
  2. Replace spaces using built-in method.
  3. Return modified string.

Dry Run

Input:s = "hello world"

Replace spaces:
"hello world"
→
"helloworld"

Final Result:
"helloworld"

Brute Force Code

Complexity Analysis

Time Complexity: O(n)Explanation:
Each character is processed once.

Space Complexity: O(n)
Explanation:
Modified string is created.

Approach 2 : Optimized Solution (Manual Traversal)

Explanation

Instead of using built-in methods, we can manually traverse the string.

The idea is:

  1. Traverse every character
  2. Ignore spaces
  3. Store only non-space characters

This helps understand filtering logic clearly.

Steps

  1. Create empty result string.
  2. Traverse all characters.
  3. If character is not space:
    • append into result
  4. Return final string.

Dry Run

Input:s = "hello world"

Traverse h:
Not space

Result:
"h"
Traverse e:
Not space

Result:
"he"

Continue traversal...

Traverse space:
Ignore character

Continue traversal...

Final Result:
"helloworld"

Optimized Code

Complexity Analysis

Time Complexity: O(n)Explanation:
Each character is traversed once.

Space Complexity: O(n)
Explanation:
Extra result string is used.
Edge Cases
  1. String contains no spaces
  2. String contains only spaces
  3. Multiple consecutive spaces
  4. String contains symbols
  5. String contains numbers

Why This Problem is Important

This problem helps in understanding:

  1. String traversal
  2. Character filtering
  3. Text cleaning
  4. Conditional processing
  5. Manual string manipulation

It is one of the most common beginner-level string interview problems.

Real-World Applications

Space removal concepts are used in:

  1. Text preprocessing
  2. Search engines
  3. Data cleaning systems
  4. NLP pipelines
  5. Input sanitization

Common Mistakes

  1. Forgetting multiple spaces
  2. Incorrect condition checks
  3. String concatenation errors
  4. Modifying non-space characters

Interview Tips

Interviewers often expect:

  1. Proper traversal logic
  2. Efficient filtering approach
  3. String manipulation understanding

Always explain why spaces are skipped during traversal.

Related Questions

  1. Reverse String
  2. Lowercase Conversion
  3. Valid Palindrome
  4. Remove Duplicates
  5. String Compression

Final Takeaway

The Remove Spaces from String problem is a fundamental string manipulation problem that teaches filtering and traversal techniques. Understanding this problem builds a strong foundation for advanced text processing and string-based interview problems.