LeetCode in Kotlin

2109. Adding Spaces to a String

Medium

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 **Y**our **C**offee".

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.

Solution

class Solution {
    fun addSpaces(s: String, spaces: IntArray): String {
        val stringChars = CharArray(s.length + spaces.size)
        for (i in spaces.indices) {
            stringChars[spaces[i] + i] = ' '
        }
        var equivalentIndex = -1
        var i = 0
        while (i < s.length) {
            equivalentIndex++
            if (stringChars[equivalentIndex] == ' ') {
                i--
            } else {
                stringChars[equivalentIndex] = s[i]
            }
            i++
        }
        return String(stringChars)
    }
}

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