reverse-string-prefix

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Algorithms

You are given a string <code>s</code> and an integer <code>k</code>.

Reverse the first <code>k</code> characters of <code>s</code> and return the resulting string.

&nbsp;
Example 1:

<div class="example-block">
Input: s = &quot;abcd&quot;, k = 2

Output: &quot;bacd&quot;

Explanation:​​​​​​​

The first <code>k = 2</code> characters <code>&quot;ab&quot;</code> are reversed to <code>&quot;ba&quot;</code>. The final resulting string is <code>&quot;bacd&quot;</code>.
</div>

Example 2:

<div class="example-block">
Input: s = &quot;xyz&quot;, k = 3

Output: &quot;zyx&quot;

Explanation:

The first <code>k = 3</code> characters <code>&quot;xyz&quot;</code> are reversed to <code>&quot;zyx&quot;</code>. The final resulting string is <code>&quot;zyx&quot;</code>.
</div>

Example 3:

<div class="example-block">
Input: s = &quot;hey&quot;, k = 1

Output: &quot;hey&quot;

Explanation:

The first <code>k = 1</code> character <code>&quot;h&quot;</code> remains unchanged on reversal. The final resulting string is <code>&quot;hey&quot;</code>.
</div>

&nbsp;
Constraints:

<ul>
	<li><code>1 &lt;= s.length &lt;= 100</code></li>
	<li><code>s</code> consists of lowercase English letters.</li>
	<li><code>1 &lt;= k &lt;= s.length</code></li>
</ul>

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reversePrefix

中级工程师

Reverse String Prefix

Two Pointers

String

给你一个字符串 <code>s</code> 和一个整数 <code>k</code>。

反转 <code>s</code> 的前 <code>k</code> 个字符，并返回结果字符串。

&nbsp;

示例 1:

<div class="example-block">
输入: s = "abcd", k = 2

输出: "bacd"

解释:

前 <code>k = 2</code> 个字符 <code>"ab"</code> 反转为 <code>"ba"</code>。最终得到的结果字符串为 <code>"bacd"</code>。
</div>

示例 2:

<div class="example-block">
输入: s = "xyz", k = 3

输出: "zyx"

解释:

前 <code>k = 3</code> 个字符 <code>"xyz"</code> 反转为 <code>"zyx"</code>。最终得到的结果字符串为 <code>"zyx"</code>。
</div>

示例 3:

<div class="example-block">
输入: s = "hey", k = 1

输出: "hey"

解释:

前 <code>k = 1</code> 个字符 <code>"h"</code> 在反转后保持不变。最终得到的结果字符串为 <code>"hey"</code>。
</div>

&nbsp;

提示:

<ul>
	<li><code>1 &lt;= s.length &lt;= 100</code></li>
	<li><code>s</code> 仅由小写英文字母组成。</li>
	<li><code>1 &lt;= k &lt;= s.length</code></li>
</ul>