## replace_copy

replace_copy

Category: algorithms

Component type: function

### Prototype

```template <class InputIterator, class OutputIterator, class T> OutputIterator replace_copy(InputIterator first, InputIterator last, OutputIterator result, const T& old_value, const T& new_value);```

### Description

Replace_copy copies elements from the range [first, last) to the range [result, result + (last-first)), except that any element equal to old_value is not copied; new_value is copied instead. More precisely, for every integer n such that 0 <= n < last-first, replace_copy performs the assignment *(result+n) = new_value if *(first+n) == old_value, and *(result+n) = *(first+n) otherwise.

### Definition

Defined in the standard header algorithm, and in the nonstandard backward-compatibility header algo.h.

### Requirements on types

• InputIterator is a model of Input Iterator.

• OutputIterator is a model of Output Iterator.

• T is EqualityComparable, and may be compared for equality with objects of InputIterator's value type.

• T is Assignable.

• T is convertible to a type in OutputIterator's set of value types.

### Preconditions

• [first, last) is a valid range.

• There is enough space in the output range to store the copied values. That is, [result, result + (last-first)) is a valid range.

• result is not an iterator within the range [first, last).

### Complexity

Linear. Replace_copy performs exactly last – first comparisons for equality and exactly last – first assignments.

### Example

```vector<int> V1; V1.push_back(1); V1.push_back(2); V1.push_back(3); V1.push_back(1); vector<int> V2(4); replace_copy(V1.begin(), V1.end(), V2.begin(), 1, 99); assert(V[0] == 99 && V[1] == 2 && V[2] == 3 && V[3] == 99);```