add leetcode problem-cn part2

算法题（国内版）/problem (English)/判定字符是否唯一(English) [is-unique-lcci].html

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+<p>Implement an algorithm to determine if a string has all unique characters. What if you cannot use additional data structures?</p>
+
+<p><strong>Example 1:</strong></p>
+
+<pre>
+<strong>Input: </strong><code>s</code> = &quot;leetcode&quot;
+<strong>Output: </strong>false
+</pre>
+
+<p><strong>Example 2:</strong></p>
+
+<pre>
+<strong>Input: </strong><code>s</code> = &quot;abc&quot;
+<strong>Output: </strong>true
+</pre>
+
+<p>&nbsp;</p>
+
+<p><strong>Note:</strong></p>
+
+<ul>
+	<li><code>0 &lt;= len(s) &lt;= 100 </code></li>
+</ul>