Adding_Spaces_to_a_String.py

# 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.


class Solution:
    def addSpaces(self, s: str, spaces: List[int]) -> str:
        # we will collect the converted string into a seperate variable
        answer = ""
        # start index needed to break s into substrings
        start = 0
        for i in range(len(spaces)):
            # break and add a space
            answer += s[start:spaces[i]] + ' '
            # update the start index to break in the next iteration
            start = spaces[i]
            # if we reached the end of spaces needed to put, we simply copy the rest of s
            if i == len(spaces) - 1:
                answer += s[start:]
                return answer