# 2109. Adding Spaces to a String

## 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

• 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;
}
};

• 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)


• 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;
}