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leetcode/1816.Truncate-Sentence/README.md

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+# [1816. Truncate Sentence](https://leetcode-cn.com/problems/truncate-sentence/)
+
+## 题目
+
+A sentence is a list of words that are separated by a single space with no leading or trailing spaces. Each of the words consists of only uppercase and lowercase English letters (no punctuation).
+
+- For example, "Hello World", "HELLO", and "hello world hello world" are all sentences.
+
+You are given a sentence s and an integer k. You want to truncate s such that it contains only the first k words. Return s after truncating it.
+
+**Example 1**:
+
+    Input: s = "Hello how are you Contestant", k = 4
+    Output: "Hello how are you"
+    Explanation:
+    The words in s are ["Hello", "how" "are", "you", "Contestant"].
+    The first 4 words are ["Hello", "how", "are", "you"].
+    Hence, you should return "Hello how are you".
+
+**Example 2**:
+
+    Input: s = "What is the solution to this problem", k = 4
+    Output: "What is the solution"
+    Explanation:
+    The words in s are ["What", "is" "the", "solution", "to", "this", "problem"].
+    The first 4 words are ["What", "is", "the", "solution"].
+    Hence, you should return "What is the solution".
+
+**Example 3**:
+
+    Input: s = "chopper is not a tanuki", k = 5
+    Output: "chopper is not a tanuki"
+
+**Constraints:**
+
+- 1 <= s.length <= 500
+- k is in the range [1, the number of words in s].
+- s consist of only lowercase and uppercase English letters and spaces.
+- The words in s are separated by a single space.
+- There are no leading or trailing spaces.
+
+## 题目大意
+
+句子 是一个单词列表，列表中的单词之间用单个空格隔开，且不存在前导或尾随空格。每个单词仅由大小写英文字母组成（不含标点符号）。
+
+- 例如，"Hello World"、"HELLO" 和 "hello world hello world" 都是句子。
+
+给你一个句子 s 和一个整数 k ，请你将 s 截断使截断后的句子仅含前 k 个单词。返回截断 s 后得到的句子。
+
+## 解题思路
+
+- 遍历字符串s，找到最后一个空格的下标end
+- 如果end为0，直接返回s,否则返回s[:end]
+
+## 代码
+
+```go
+package leetcode
+
+func truncateSentence(s string, k int) string {
+	end := 0
+	for i := range s {
+		if k > 0 && s[i] == ' ' {
+			k--
+		}
+		if k == 0 {
+			end = i
+			break
+		}
+	}
+	if end == 0 {
+		return s
+	}
+	return s[:end]
+}
+```