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# 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.

### 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);
```