Creating, reading and updating an array

This chapter is about the how: the everyday code you write with arrays. Every snippet comes in JavaScript, Python, Java and C++ — pick your language on any code box and the site remembers it for every lesson.

The anatomy of an array access

The expression nums[2] = 9. The name nums refers to the whole array, the index 2 picks the third slot, and 9 is the value written there, replacing 7.

Read nums[2] aloud as "nums at index 2". Indexes count from 0, which feels odd at first: the index is really a distance from the start, and the first element is zero steps away. The last element of an array of length n is therefore at index n - 1.

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Creating an array
Reading and updating
Adding and removing at the end
The cost of each operation

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Creating, reading and updating an array

The anatomy of an array access

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