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"
andspaces = [5, 9]
, we place spaces before'Y'
and'C'
, which are at indices5
and9
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.
Solution: Scan orignal string / Two Pointers
Just scan the original string and insert a space if the current index matched the front space index.
Time complexity: O(n)
Space complexity: O(m+n) / O(1)
C++
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// Author: Huahua class Solution { public: string addSpaces(string s, vector<int>& spaces) { const int m = spaces.size(); string ans; for (int i = 0, j = 0; i < s.length(); ++i) { if (j < m && i == spaces[j]) { ans += " "; ++j; } ans += s[i]; } return ans; } }; |
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