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43 lines
1.7 KiB
HTML
43 lines
1.7 KiB
HTML
<p>Design a map that allows you to do the following:</p>
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<ul>
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<li>Maps a string key to a given value.</li>
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<li>Returns the sum of the values that have a key with a prefix equal to a given string.</li>
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</ul>
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<p>Implement the <code>MapSum</code> class:</p>
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<ul>
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<li><code>MapSum()</code> Initializes the <code>MapSum</code> object.</li>
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<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>
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<li><code>int sum(string prefix)</code> Returns the sum of all the pairs' value whose <code>key</code> starts with the <code>prefix</code>.</li>
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</ul>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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<pre>
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<strong>Input</strong>
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["MapSum", "insert", "sum", "insert", "sum"]
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[[], ["apple", 3], ["ap"], ["app", 2], ["ap"]]
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<strong>Output</strong>
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[null, null, 3, null, 5]
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<strong>Explanation</strong>
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MapSum mapSum = new MapSum();
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mapSum.insert("apple", 3);
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mapSum.sum("ap"); // return 3 (<u>ap</u>ple = 3)
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mapSum.insert("app", 2);
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mapSum.sum("ap"); // return 5 (<u>ap</u>ple + <u>ap</u>p = 3 + 2 = 5)
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</pre>
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<p> </p>
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<p><strong>Constraints:</strong></p>
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<ul>
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<li><code>1 <= key.length, prefix.length <= 50</code></li>
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<li><code>key</code> and <code>prefix</code> consist of only lowercase English letters.</li>
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<li><code>1 <= val <= 1000</code></li>
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<li>At most <code>50</code> calls will be made to <code>insert</code> and <code>sum</code>.</li>
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</ul>
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