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next_permutation

Popularity：277 ℃/2024-08-16 10:27:57

utilizationnext_permutation The function is very simple, here are the exact steps and notes:

Steps:

  1. Include header files: Make sure to include<algorithm> header file, because thenext_permutation function is located in this header file.

    #include <algorithm>

  2. Preparing the container：next_permutation can be used to handle any container that supports random access iterators, such as thevector maybestring。

    vector<int> nums = {3, 1, 4};

    If you are dealing with strings, you can do this:

    string str = "abc";

  3. Sorting (optional): In order to generate the next permutation in dictionary order, it is usually necessary to sort the container first.

    sort((), ());
// Or sorting a string
sort((), ());

  4. Cyclic generation of permutations: Usedo-while loop or other appropriate loop structure to repeatedly call thenext_permutation。

    do {
    // Process the currently generated alignment
    // Export, save, or perform other operations
} while (next_permutation((), ())));

    Or for strings:

    do {
    // Process the currently generated alignment
    // Export, save, or perform other operations
} while (next_permutation((), ())));

  5. Processing of generated alignments: Inside the loop, desired operations can be performed on each of the generated alignments, such as outputting to standard output, saving to a container, or performing other calculations.

Caveats:

  • arrange in order: Usually when usingnext_permutation The container needs to be sorted beforehand to ensure that the resulting arrangement is in dictionary order.
  • return value：next_permutation The function returns a boolean value indicating whether the next permutation was successfully generated. When the next permutation is generated it returnstrue, return when it is already the last arrangementfalse。
  • Modify the container：next_permutation function will directly modify the incoming container to generate the next arrangement.

Example:

Here is a complete example demonstrating how to use thenext_permutation Generate and process alignments:

#include <iostream>;
#include <algorithm>.
#include <vector>.

using namespace std.

int main() {
    // Prepare the data
    vector<int> nums = {3, 1, 4};

    // Sort the data to create a dictionary order
    sort((), ()); // sort the data in order to generate a dictionary order.

    // Loop over the orderings and process them
    do {
        // Process the currently generated ordering, simply outputting it to the console here.
        for (int num : nums) {
            cout << num << " ";;
        }
        cout << endl;
    } while (next_permutation((), ())).

    return 0;
}

In this example, thenums The vector contains {3, 1, 4}, which is sorted to produce a dictionary-ordered permutation.do-while The loop keeps callingnext_permutation to generate and output all possible permutations until no larger permutation can be generated.

In this way, alignment-related problems can be easily handled by utilizing thenext_permutation functions to generate and process permutations is an effective tool for solving problems such as combinatorial optimization.

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