Arrays/Java/Repeatedly Remove - Revision history

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← Older revision		Revision as of 03:16, 9 October 2019
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	==The Code==		==The Code==

	Link to git.charlesreid1.com repository: https://charlesreid1.com~~:3000~~/cs/java/src/master/arrays/sequential-remove/SequentialRemove.java		Link to git.charlesreid1.com repository: https://git.charlesreid1.com/cs/java/src/master/arrays/sequential-remove/SequentialRemove.java

	Here is the implementation code:		Here is the implementation code:

Admin: /* The Code */

2017-06-05T22:36:03Z

The Code

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			=Flags=

	[[Category:Arrays]]		[[Category:Arrays]]
	[[Category:Java]]		[[Category:Java]]
	[[Category:Random]]		[[Category:Random]]
			[[Category:Shuffle]]

			{{DataStructuresFlag}}

Admin at 22:35, 5 June 2017

2017-06-05T22:35:42Z

← Older revision		Revision as of 22:35, 5 June 2017
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			==Question==

	Question from Goodrich et al, Data Structures in Java, Chapter 3: Arrays and Lists		Question from Goodrich et al, Data Structures in Java, Chapter 3: Arrays and Lists

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	Last, remove the items from the original array in the order [2, 1, 0]. (Remove them by setting to null or 0.)		Last, remove the items from the original array in the order [2, 1, 0]. (Remove them by setting to null or 0.)

			==The Code==

			Link to git.charlesreid1.com repository: https://charlesreid1.com:3000/cs/java/src/master/arrays/sequential-remove/SequentialRemove.java

			Here is the implementation code:

			<pre>
			public static void selectAndRemove() {
			String[] a = {"A","B","C","D","E","F","G"};
			Integer[] indices = new Integer[a.length];

			// Start by populating an array of index values
			for(int i=0; i<indices.length; i++) {
			indices[i] = i;
			}

			// Create new shuffled order
			shuffle(indices);

			// Remove each item, one at a time.
			for(int i=0; i<indices.length; i++) {
			int rmi = indices[i];
			a[rmi] = null;
			System.out.printf("Removed item %d. New String array: %s \n", rmi, Arrays.toString(a));
			}
			}
			</pre>

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Question from Goodrich et al, Data Structures in Java, Chapter 3: Arrays and Lists

Question 3.2: Write a Java method that repeatedly selects and removes a random entry from an array until the array holds no more entries.

We can first create an array of sequential integer indices, then we can utilize the Fisher Yates method to shuffle this array of indexes.

For example, to shuffle an array holding integers [5, 44, 89]:

First, generate an array of sequential integer indices: [0, 1, 2]

Now, use the Fisher Yates method to shuffle these: [2, 1, 0]

Last, remove the items from the original array in the order [2, 1, 0]. (Remove them by setting to null or 0.)

[[Category:Arrays]]
[[Category:Java]]
[[Category:Random]]