102 lines
3.9 KiB
Markdown
102 lines
3.9 KiB
Markdown
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---
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title: Nesting For Loops
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---
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## Nesting For Loops
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<strong>Remember to use Read-Search-Ask if you get stuck. Try to pair program :busts_in_silhouette: and write your own code :pencil:</strong>
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:checkered_flag: <strong>Problem Explanation:</strong>
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If you have a multi-dimensional array, you can use the same logic as the prior waypoint to loop through both the array and any sub-arrays.
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Here is an example:
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```
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var arr = [
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[1,2], [3,4], [5,6]
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];
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for (var i=0; i < arr.length; i++) {
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for (var j=0; j < arr[i].length; j++) {
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console.log(arr[i][j]);
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}
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}
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```
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This outputs each sub-element in <code>arr</code> one at a time. Note that for the inner loop, we are checking the length of arr[i], since arr[i] is itself an array.
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<ul>
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<li>Modify function <code>multiplyAll</code> so that it multiplies the <code>product</code> variable by each number in the sub-arrays of <code>arr</code>.</li>
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<li>Make sure the second for loop is nested inside the first.</li>
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</ul>
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<strong>Relevant Links</strong>
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<ul>
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<li><a href="https://guide.freecodecamp.org/certifications/javascript-algorithms-and-data-structures/basic-javascript/nest-one-array-within-another-array">Nest One Array Within Another Array</a></li>
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<li><a href="https://learn.freecodecamp.org/javascript-algorithms-and-data-structures/basic-javascript/iterate-through-an-array-with-a-for-loop">Iterate Through An Array With A For Loop</a></li>
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<li><a href="https://learn.freecodecamp.org/javascript-algorithms-and-data-structures/basic-javascript/accessing-nested-arrays">Accessing Nested Arrays</a></li>
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</ul>
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:speech_balloon: Hint: 1
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Make sure to check with <code>length</code> and not the overall array.
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<em>try to solve the problem now</em>
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:speech_balloon: Hint 2<br>
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Use both <code>i</code> and <code>j</code> when multiplying the product.
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<em>try to solve the problem now</em>
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:speech_balloon: Hint 3<br>
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Remember to use <code>arr[i]</code> when you multiply the sub-arrays with the <code>product</code> variable.
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<em>try to solve the problem now</em>
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<em>Spoiler Alert!</em>
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<img src="https://discourse-user-assets.s3.amazonaws.com/original/2X/2/2d6c412a50797771301e7ceabd554cef4edcd74d.gif">
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<br>
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<strong>Solution Ahead!</strong>
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:beginner: <strong>Basic Code Solution:</strong>
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```
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function multiplyAll(arr) {
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var product = 1;
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// Only change code below this line
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for(var i=0; i < arr.length; i++){
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for (var j=0; j < arr[i].length; j++){
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product = product * arr[i][j];
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}
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}
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// Only change code above this line
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return product;
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}
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// Modify values below to test your code
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multiplyAll([[1,2],[3,4],[5,6,7]]);
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```
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:rocket: <strong><a href="https://learn.freecodecamp.org/javascript-algorithms-and-data-structures/basic-javascript/nesting-for-loops/">Run Code</a></strong>
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<strong>Code Explanation:</strong>
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<ul>
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<li>We check the length of <code>arr</code> in the <code>i</code> for loop and the <code>arr[i]</code> length in the <code>j</code> for loop.</li>
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<li>We multiply the <code>product</code> variable by itself because it equals 1, and then multiply it by the sub-arrays.</li>
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<li>The two sub-arrays to multiply are <code>arr[i]</code> and <code>j</code>.</li>
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</ul>
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:clipboard: <strong>NOTES FOR CONTRIBUTIONS:</strong>
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<ul>
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<li>:warning: <strong>DO NOT</strong> add solutions that are similar to any existing solutions. If you think it is similar but better, then try to merge (or replace) the existing similar solution.</li>
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<li>Add an explanation of your solution.</li>
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<li>Categorize the solution in one of the following categories — Basic, Intermediate and Advanced. :traffic_light:</li>
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<li>Please add your username only if you have added any relevant main contents. (:warning: <em><strong>DO NOT</strong></em> remove any existing usernames)</li>
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</ul>
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See :point_right: <a href="http://forum.freecodecamp.com/t/algorithm-article-template/14272"> Wiki Challenge Solution Template</a> for reference.
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