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2109. Adding Spaces to a String

MediumOpen on LeetCodeProblem statement

Problem Statement

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.

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:

Java — stringBuilder

Source file
class Solution {
    public String addSpaces(String s, int[] spaces) {
        StringBuilder sb = new StringBuilder(s.substring(0, spaces[0]));
        for (int i = 1; i < spaces.length; i++)
            sb.append(" ").append(s.substring(spaces[i - 1], spaces[i]));
        sb.append(" ").append(s.substring(spaces[spaces.length - 1]));
        return sb.toString();
    }
}