---
tags: LeetCode
---

# 557. Reverse Words in a String III
Given a string, you need to reverse the order of characters in each word within a sentence while still preserving whitespace and initial word order.

Example 1:

Input: "Let's take LeetCode contest" 
Output: "s'teL ekat edoCteeL tsetnoc"

Note: In the string, each word is separated by single space and there will not be any extra space in the string.

輸入範本如下

public class Solution {
    public string ReverseWords(string s) {
        
    }
}

#### 自我限制
不准使用 Join , Spilt , Reverse , Aggregat 等方法

116 ms	34.9 MB
You are here!
Your runtime beats 36.87 % of csharp submissions.
public string ReverseWords(string s)
{
    return string.Join(" ", s.Trim().Split(' ').Select(word => new string(word.Reverse().ToArray())));
}

116 ms	34.9 MB
You are here!
Your runtime beats 36.87 % of csharp submissions.
public string ReverseWords(string s)
{
    var build = s.Split(' ').Select(word => new string(word.Reverse().ToArray())).Aggregate(new StringBuilder(), (builder, word) => builder.Append(word + " "));
    return build.ToString().Trim();
}

### 直覺想法
字與字之間是使用空白字元去間隔的 , 因此只要發現空白字元的時候 , 就去反轉之前發現的字元

儲存媒介使用 StringBuilder or char[] , 效果差不多.

84 ms	31.1 MB
You are here!
Your runtime beats 97.64 % of csharp submissions.
public string ReverseWords(string s)
{
    StringBuilder stringBuilder = new StringBuilder(s);
    for (int left = 0, right = 0; right < s.Length; left = ++right)
    {
        while (right < s.Length && s[right] != ' ')
        {
            right++;
        }
        Swap(stringBuilder, left, right - 1);
    }
    return stringBuilder.ToString().Trim();

    void Swap(StringBuilder builder, int l, int r)
    {
        for (; l < r; l++, r--)
        {
            char temp = builder[l];
            builder[l] = builder[r];
            builder[r] = temp;
        }
    }
}

84 ms	31 MB
You are here!
Your runtime beats 97.64 % of csharp submissions.
public string ReverseWords(string s)
{
    var cArr = s.ToCharArray();
    for (int left = 0, right = 0; right < cArr.Length; left = ++right)
    {
        while (right < cArr.Length && cArr[right] != ' ')
        {
            right++;
        }
        Swap(cArr, left, right - 1);
    }
    return new string(cArr).Trim();

    void Swap(char[] arr, int l, int r)
    {
        for (; l < r; l++, r--)
        {
            char temp = arr[l];
            arr[l] = arr[r];
            arr[r] = temp;
        }
    }
}

### Thank you!

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