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The time complexity of deleting from an array depends on **where the element is deleted from**: the end, the start, or the middle.

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### **1. Deleting from the end of an array**

- The last element is simply removed.
- Nothing needs to be shifted.
**Complexity: O(1)**, constant time.

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### **2. Deleting from the start or middle of an array**

- After the deletion, a "hole" forms.
- All elements to the right of it need to be **shifted left** to fill the empty spot.

For example:

```javascript
[1, 2, 3, 4, 5]
delete 2 → [1, 3, 4, 5]
```

`[3, 4, 5]` get shifted, 3 elements.
In the worst case (if the first element is deleted), almost the entire array has to be shifted.

**Complexity: O(n)**, linear time.

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### **3. Formally**

| Deletion type | Complexity |
|---|---|
| From the end | **O(1)** |
| From the start or middle | **O(n)** |

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### **4. Why**

An array is a **contiguous block of memory**, so an element cannot be "cut out" without shifting the rest.
This is how it differs from a **linked list**, where deletion by reference runs in O(1).

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**Summary:**

> Deleting from the end of an array is fast (**O(1)**),
> from the middle or start it's slow (**O(n)**), because it requires shifting the remaining elements.

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