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.

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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.

依次遍歷即可，用stringbuilder 記錄，最后導(dǎo)出即可，不理解為什么是中等題目，不應(yīng)該是簡(jiǎn)單題目嗎？

Runtime:?35 ms, faster than?58.22%?of?Java?online submissions for?Adding Spaces to a String.

Memory Usage:?76.4 MB, less than?72.89%?of?Java?online submissions for?Adding Spaces to a String.

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