Home >Backend Development >PHP Tutorial >Adding Spaces to a String

Adding Spaces to a String

Patricia Arquette
Patricia ArquetteOriginal
2024-12-22 20:23:11251browse

Adding Spaces to a String

2109. Adding Spaces to a String

Difficulty: Medium

Topics: Array, Two Pointers, String, Simulation

You are given a 0-indexed string s and a 0-indexed integer array spaces that describes the indices in the original string where spaces will be added. Each space should be inserted before the character at the given index.

  • For example, given s = "EnjoyYourCoffee" and spaces = [5, 9], we place spaces before 'Y' and 'C', which are at indices 5 and 9 respectively. Thus, we obtain "Enjoy Your Coffee".

Return the modified string after the spaces have been added.

Example 1:

  • Input: s = "LeetcodeHelpsMeLearn", spaces = [8,13,15]
  • Output: "Leetcode Helps Me Learn"
  • Explanation: The indices 8, 13, and 15 correspond to the underlined characters in "LeetcodeHelpsMeLearn".
    • We then place spaces before those characters.

Example 2:

  • Input: s = "icodeinpython", spaces = [1,5,7,9]
  • Output: "i code in py thon"
  • Explanation: The indices 1, 5, 7, and 9 correspond to the underlined characters in "icodeinpython".
    • We then place spaces before those characters.

Example 3:

  • Input: s = "spacing", spaces = [0,1,2,3,4,5,6]
  • Output: " s p a c i n g"
  • Explanation: We are also able to place spaces before the first character of the string.

Constraints:

  • 1 <= s.length <= 3 * 105
  • s consists only of lowercase and uppercase English letters.
  • 1 <= spaces.length <= 3 * 105
  • 0 <= spaces[i] <= s.length - 1
  • All the values of spaces are strictly increasing.

Hint:

  1. Create a new string, initially empty, as the modified string. Iterate through the original string and append each character of the original string to the new string. However, each time you reach a character that requires a space before it, append a space before appending the character.
  2. Since the array of indices for the space locations is sorted, use a pointer to keep track of the next index to place a space. Only increment the pointer once a space has been appended.
  3. Ensure that your append operation can be done in O(1).

Solution:

We can use an efficient approach with two pointers. Here's how the implementation in PHP 5.6 would look:

Solution Explanation:

  1. Use a pointer spaceIndex to track the current position in the spaces array.
  2. Iterate through the string s using a loop.
  3. Check whether the current index in the string matches the current value in the spaces array. If it does, append a space to the result and move the spaceIndex pointer forward.
  4. Append the current character of the string to the result.
  5. Return the final result as a single string.

This approach ensures that we process the input efficiently, taking advantage of the sorted order of the spaces array.

Let's implement this solution in PHP: 2109. Adding Spaces to a String






Explanation:

  1. Efficient Appending: The . operator in PHP is used to append strings efficiently.
  2. Two Pointers: The spaceIndex pointer ensures we only process the spaces array once.
  3. Time Complexity:
    • Iterating over the string takes O(n), where n is the length of the string.
    • Checking against the spaces array pointer takes O(m), where m is the length of the spaces array.
    • Combined: O(n m), which is optimal given the constraints.

This solution adheres to the constraints and is efficient even for large inputs.

Contact Links

If you found this series helpful, please consider giving the repository a star on GitHub or sharing the post on your favorite social networks ?. Your support would mean a lot to me!

If you want more helpful content like this, feel free to follow me:

  • LinkedIn
  • GitHub

The above is the detailed content of Adding Spaces to a String. For more information, please follow other related articles on the PHP Chinese website!

Statement:
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn