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43 lines
1.6 KiB
HTML
43 lines
1.6 KiB
HTML
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<p>Given an integer array <code>arr</code> and a filtering function <code>fn</code>, return a new array with a fewer or equal number of elements.</p>
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<p>The returned array should only contain elements where <code>fn(arr[i], i)</code> evaluated to a truthy value.</p>
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<p>Please solve it without the built-in <code>Array.filter</code> method.</p>
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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> arr = [0,10,20,30], fn = function greaterThan10(n) { return n > 10; }
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<strong>Output:</strong> [20,30]
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<strong>Explanation:</strong>
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const newArray = filter(arr, fn); // [20, 30]
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The function filters out values that are not greater than 10</pre>
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<p><strong class="example">Example 2:</strong></p>
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<pre>
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<strong>Input:</strong> arr = [1,2,3], fn = function firstIndex(n, i) { return i === 0; }
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<strong>Output:</strong> [1]
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<strong>Explanation:</strong>
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fn can also accept the index of each element
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In this case, the function removes elements not at index 0
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</pre>
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<p><strong class="example">Example 3:</strong></p>
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<pre>
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<strong>Input:</strong> arr = [-2,-1,0,1,2], fn = function plusOne(n) { return n + 1 }
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<strong>Output:</strong> [-2,0,1,2]
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<strong>Explanation:</strong>
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Falsey values such as 0 should be filtered out
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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>0 <= arr.length <= 1000</code></li>
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<li><code><font face="monospace">-10<sup>9</sup> <= arr[i] <= 10<sup>9</sup></font></code></li>
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</ul>
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