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<!--replace-end-7--><!--replace-end-4--><!--replace-end-1--></head><body><div class="ui fluid container universe"><!--replace-start-2--><!--replace-start-3--><!--replace-start-6--><div class="ui text container" id="zettel-container" style="position: relative"><div class="zettel-view"><article class="ui raised attached segment zettel-content"><div class="pandoc"><h1 id="title-h1">Sliding window</h1><p>Whereas the <span class="zettel-link-container cf"><span class="zettel-link" title="Zettel: Multiple pointers"><a href="Multiple_pointers.html">multiple pointer</a></span></span> pattern works by keeping two array indices running at once and comparing their values on each iteration, the sliding window has a running value (the ‘window’) that is updated at each iteration and which compares itself against its most recent previous value.</p><p>This is what makes it ‘sliding’: the value isn’t constant, it changes (or doesn’t) based on what it was previously.</p><h2 id="example-maximum-sum-of-sub-array">Example: maximum sum of sub-array</h2><p>We create a function that takes an array and a sub-array length <em>n</em>. The objective is to find the maximum value that can be created by summing <em>n</em> elements of the array. It moves through the array, summing by <em>n</em> keeping track of the highest sum value so far and the current sum value. At the end it should return the highest possible sum value.</p><p>Here we do this for a sub-array of length 2:</p><pre><code class="ts language-ts">function maxSubarraySum(arr, subArrLength) {
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let maxSum = 0; // Largest sum value so far
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let tempSum = 0; // Current sum value
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// Establish the first 'maxSum'
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// At the beginning this will just be the sum of the first two array elements
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for (let i = 0; i < subArrLength; i++) {
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maxSum += arr[i];
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}
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// Map temporary sum to maxSum
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// Accordingly, as we have only mapped the first sub-array, the max sum will be the same
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// as the current sum
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tempSum = maxSum;
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// Move through the array one element at a time (`i++`) via a window starting from the element that is equal to `subArrLength`
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// The first sum calculation is already taken care of in the earlier loop and stored in `maxSum`, so we don't have to worry about missing the elements in indices less than subArrLength
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for (let i = subArrLength; i < arr.length; i++) {
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// Temp sum becomes a moveable window value equal to the subtraction of the previous element and the addition of next element in line
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tempSum = tempSum - arr[i - subArrLength] + arr[i];
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// Max sum is redefined as the largest subArrLengthber between the previous highest and the current value of tempSum
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maxSum = Math.max(maxSum, tempSum);
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return maxSum;
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}
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console.log(maxSubarraySum([100, 200, 300, 400], 2)); // 700</code></pre></div></article><nav class="ui attached segment deemphasized bottomPane" id="neuron-tags-pane"><div><span class="ui basic label zettel-tag" title="Tag">design-patterns</span></div></nav><nav class="ui bottom attached icon compact inverted menu blue" id="neuron-nav-bar"><!--replace-start-9--><!--replace-end-9--><a class="right item" href="impulse.html" title="Open Impulse"><i class="wave square icon"></i></a></nav></div></div><!--replace-end-6--><!--replace-end-3--><!--replace-end-2--><div class="ui center aligned container footer-version"><div class="ui tiny image"><a href="https://neuron.zettel.page"><img alt="logo" src="https://raw.githubusercontent.com/srid/neuron/master/assets/neuron.svg" title="Generated by Neuron 1.9.35.3" /></a></div></div></div></body></html> |