# C++ Algorithm replace()

C++ Algorithm replace() function is used to replace all value equal to old_value by the value new_value in the range [first, last).

This function examines each element in the range and replaces it if it matches a specified value.

## Parameter

first: A forward iterator pointing to the initial position in the range from which elements are being replaced.

last: A forward iterator pointing to the final position in the range from which elements are being replaced.

old_value: The old value of the elements to be replaced.

new_value: The new value being assigned to the elements with the old value.

None

## Complexity

Complexity is linear in the distance within first and last. It compares each element and assigns to those matching.

## Data races

The objects in the range [first1, last1) are accessed and potentially modified.

## Exception safety

Throws an exception if any of the function calls the assignments or the operations on iterators throws an exception.

Please note that invalid parameters cause an undefined behavior.

## Example 1

Let's see the simple example to demonstrate the use of replace():

Output:

```3,10,2,10,2,
```

In the above example, element 1 of vector v is replaced by 10.

## Example 2

Let's see another simple example:

Output:

```The original vector v1 is:
( 4 7 7 7 0 5 7 1 6 9 3 7 8 2 ).
The vector v1 with a value 700 replacing that of 7 is:
( 4 700 700 700 0 5 700 1 6 9 3 700 8 2 ).
```

In the above example, replace() finds all the elements from vector v1 matches with 7 and replace it with the 700.

## Example 3

Let's see another simple example:

Output:

```v : 1 4 3 2 3 10 7 9 3 8
After replacing 3 with 6
v : 1 4 6 2 6 10 7 9 6 8
```

## Example 4

Let's see another simple example:

Output:

```myvector contains: 10 99 30 30 99 10 10 99
```

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