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website/content/ChapterFour/0151.Reverse-Words-in-a-String.md

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+# [151. Reverse Words in a String](https://leetcode.com/problems/reverse-words-in-a-string/)
+
+
+
+## 题目
+
+Given an input string, reverse the string word by word.
+
+**Example 1**:
+
+    Input: "the sky is blue"
+    Output: "blue is sky the"
+
+**Example 2**:
+
+    Input: "  hello world!  "
+    Output: "world! hello"
+    Explanation: Your reversed string should not contain leading or trailing spaces.
+
+**Example 3**:
+
+    Input: "a good   example"
+    Output: "example good a"
+    Explanation: You need to reduce multiple spaces between two words to a single space in the reversed string.
+
+**Note**:
+
+- A word is defined as a sequence of non-space characters.
+- Input string may contain leading or trailing spaces. However, your reversed string should not contain leading or trailing spaces.
+- You need to reduce multiple spaces between two words to a single space in the reversed string.
+
+**Follow up**:
+
+For C programmers, try to solve it *in-place* in *O*(1) extra space.
+
+
+## 题目大意
+
+给定一个字符串，逐个翻转字符串中的每个单词。
+
+说明：
+
+- 无空格字符构成一个单词。
+- 输入字符串可以在前面或者后面包含多余的空格，但是反转后的字符不能包括。
+- 如果两个单词间有多余的空格，将反转后单词间的空格减少到只含一个。
+ 
+
+进阶：
+
+- 请选用 C 语言的用户尝试使用 O(1) 额外空间复杂度的原地解法。
+
+
+## 解题思路
+
+
+- 给出一个中间有空格分隔的字符串，要求把这个字符串按照单词的维度前后翻转。
+- 依照题意，先把字符串按照空格分隔成每个小单词，然后把单词前后翻转，最后再把每个单词中间添加空格。
+
+
+## 代码
+
+```go
+
+package leetcode
+
+import "strings"
+
+func reverseWords151(s string) string {
+	ss := strings.Fields(s)
+	reverse151(&ss, 0, len(ss)-1)
+	return strings.Join(ss, " ")
+}
+
+func reverse151(m *[]string, i int, j int) {
+	for i <= j {
+		(*m)[i], (*m)[j] = (*m)[j], (*m)[i]
+		i++
+		j--
+	}
+}
+
+```