all permutations with repetition C++

To generate all permutations with repetition in C++, you can use the std::next_permutation function from the <algorithm> library. This function generates the next lexicographically greater permutation of a sequence, which allows you to generate all possible permutations by repeatedly calling it.

Here are the steps to generate all permutations with repetition in C++:

1. Include the necessary libraries:

#include <iostream>
#include <algorithm>
#include <vector>

1. Define the input sequence:

std::vector<int> sequence = {1, 2, 2, 3};

1. Sort the sequence:

std::sort(sequence.begin(), sequence.end());

Sorting the sequence is necessary for the std::next_permutation function to work correctly.

1. Generate permutations:

do {
    // Print or process the current permutation
    for (int num : sequence) {
        std::cout << num << " ";
    }
    std::cout << std::endl;
} while (std::next_permutation(sequence.begin(), sequence.end()));

In the code above, the do-while loop repeatedly calls std::next_permutation to generate the next permutation. It also prints or processes the current permutation. The loop continues until std::next_permutation returns false, indicating that all permutations have been generated.

Here's the complete code:

#include <iostream>
#include <algorithm>
#include <vector>

int main() {
    std::vector<int> sequence = {1, 2, 2, 3};
    std::sort(sequence.begin(), sequence.end());

    do {
        for (int num : sequence) {
            std::cout << num << " ";
        }
        std::cout << std::endl;
    } while (std::next_permutation(sequence.begin(), sequence.end()));

    return 0;
}

This code will output all permutations with repetition of the input sequence {1, 2, 2, 3}. The std::sort function ensures that the sequence is sorted in ascending order before generating the permutations.

I hope this explanation helps! Let me know if you have any further questions.