# A data structure for n elements and O(1) operations

Propose a data structure for the following:
The data structure would hold elements from 0 to n-1. There is no order on the elements (no ascending/descending order requirement)

The complexity of the operations should be as follows:
* Insertion of an element – O(1)
* Deletion of an element – O(1)
* Finding an element – O(1)

We strongly recommend to minimize the browser and try this yourself first.

A boolean array works here. Array will have value ‘true’ at ith index if i is present, and ‘false’ if absent.

Initialization:
We create an array of size n and initialize all elements as absent.

 `void` `initialize(``int` `n) ` `{ ` `  ``bool` `A[n]; ` `  ``for` `(``int` `i = 0; i

Insertion of an element:

 `void` `insert(unsigned i) ` `{ ` `   ``/* set the value at index i to true */` `   ``A[i] = 1; ``// Or A[i] = true; ` `} `

Deletion of an element:

 `void` `delete``(unsigned i) ` `{ ` `  ``/* make the value at index i to 0 */` `  ``A[i] = 0;  ``// Or A[i] = false; ` `} `

Finding an element:

 `// Returns true if 'i' is present, else false ` `bool` `find(unsigned i) ` `{ ` `    ``return` `A[i]; ` `} `

As an exercise, change the data structure so that it holds values from 1 to n instead of 0 to n-1.

This article is contributed by Sachin. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above

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