Question

2109. Adding Spaces to a String

中文文档

Description

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.

Solutions

Solution 1

class Solution:
  def addSpaces(self, s: str, spaces: List[int]) -> str:
    ans = []
    j = 0
    for i, c in enumerate(s):
      if j < len(spaces) and i == spaces[j]:
        ans.append(' ')
        j += 1
      ans.append(c)
    return ''.join(ans)

class Solution {
  public String addSpaces(String s, int[] spaces) {
    StringBuilder ans = new StringBuilder();
    for (int i = 0, j = 0; i < s.length(); ++i) {
      if (j < spaces.length && i == spaces[j]) {
        ans.append(' ');
        ++j;
      }
      ans.append(s.charAt(i));
    }
    return ans.toString();
  }
}

class Solution {
public:
  string addSpaces(string s, vector<int>& spaces) {
    string ans = "";
    for (int i = 0, j = 0; i < s.size(); ++i) {
      if (j < spaces.size() && i == spaces[j]) {
        ans += ' ';
        ++j;
      }
      ans += s[i];
    }
    return ans;
  }
};

func addSpaces(s string, spaces []int) string {
  var ans []byte
  for i, j := 0, 0; i < len(s); i++ {
    if j < len(spaces) && i == spaces[j] {
      ans = append(ans, ' ')
      j++
    }
    ans = append(ans, s[i])
  }
  return string(ans)
}

function addSpaces(s: string, spaces: number[]): string {
  let ans = '';
  for (let i = 0, j = 0; i < s.length; i++) {
    if (j < spaces.length && i === spaces[j]) {
      ans += ' ';
      ++j;
    }
    ans += s[i];
  }
  return ans;
}

Solution 2

class Solution:
  def addSpaces(self, s: str, spaces: List[int]) -> str:
    ans = []
    i, j = len(s) - 1, len(spaces) - 1
    while i >= 0:
      ans.append(s[i])
      if j >= 0 and i == spaces[j]:
        ans.append(' ')
        j -= 1
      i -= 1
    return ''.join(ans[::-1])