# 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<n; i++) ` ` ` `A[i] = {0}; ` `// or A[n] = {false}; ` `} ` |

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**Insertion of an element:**

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

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**Deletion of an element:**

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

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** Finding an element:**

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

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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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