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leetcode/problem/map-sum-pairs.html

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+<p>Design a map that allows you to do the following:</p>
+
+<ul>
+	<li>Maps a string key to a given value.</li>
+	<li>Returns the sum of the values that have a key with a prefix equal to a given string.</li>
+</ul>
+
+<p>Implement the <code>MapSum</code> class:</p>
+
+<ul>
+	<li><code>MapSum()</code> Initializes the <code>MapSum</code> object.</li>
+	<li><code>void insert(String key, int val)</code> Inserts the <code>key-val</code> pair into the map. If the <code>key</code> already existed, the original <code>key-value</code> pair will be overridden to the new one.</li>
+	<li><code>int sum(string prefix)</code> Returns the sum of all the pairs&#39; value whose <code>key</code> starts with the <code>prefix</code>.</li>
+</ul>
+
+<p>&nbsp;</p>
+<p><strong>Example 1:</strong></p>
+
+<pre>
+<strong>Input</strong>
+[&quot;MapSum&quot;, &quot;insert&quot;, &quot;sum&quot;, &quot;insert&quot;, &quot;sum&quot;]
+[[], [&quot;apple&quot;, 3], [&quot;ap&quot;], [&quot;app&quot;, 2], [&quot;ap&quot;]]
+<strong>Output</strong>
+[null, null, 3, null, 5]
+
+<strong>Explanation</strong>
+MapSum mapSum = new MapSum();
+mapSum.insert(&quot;apple&quot;, 3);  
+mapSum.sum(&quot;ap&quot;);           // return 3 (<u>ap</u>ple = 3)
+mapSum.insert(&quot;app&quot;, 2);    
+mapSum.sum(&quot;ap&quot;);           // return 5 (<u>ap</u>ple + <u>ap</u>p = 3 + 2 = 5)
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= key.length, prefix.length &lt;= 50</code></li>
+	<li><code>key</code> and <code>prefix</code> consist of only lowercase English letters.</li>
+	<li><code>1 &lt;= val &lt;= 1000</code></li>
+	<li>At most <code>50</code> calls will be made to <code>insert</code> and <code>sum</code>.</li>
+</ul>