在C++中查找排列和组合

#include <iostream>
#include <vector>

using namespace std;

// 递归方式查找排列
void findPermutations(vector<int>& nums, vector<int>& permutation, vector<bool>& used, vector<vector<int>>& result) {
    if (permutation.size() == nums.size()) {
        result.push_back(permutation);
        return;
    }

    for (int i = 0; i < nums.size(); i++) {
        if (used[i]) continue;
        used[i] = true;
        permutation.push_back(nums[i]);
        findPermutations(nums, permutation, used, result);
        permutation.pop_back();
        used[i] = false;
    }
}

// 递归方式查找组合
void findCombinations(vector<int>& nums, int start, int k, vector<int>& combination, vector<vector<int>>& result) {
    if (k == 0) {
        result.push_back(combination);
        return;
    }

    for (int i = start; i <= nums.size() - k; i++) {
        combination.push_back(nums[i]);
        findCombinations(nums, i + 1, k - 1, combination, result);
        combination.pop_back();
    }
}

int main() {
    vector<int> nums = {1, 2, 3};
    vector<vector<int>> permutations;
    vector<vector<int>> combinations;

    vector<int> permutation;
    vector<bool> used(nums.size(), false);
    findPermutations(nums, permutation, used, permutations);

    for (int k = 1; k <= nums.size(); k++) {
        vector<int> combination;
        findCombinations(nums, 0, k, combination, combinations);
    }

    cout << "Permutations:" << endl;
    for (const auto& p : permutations) {
        for (const auto& num : p) {
            cout << num << " ";
        }
        cout << endl;
    }

    cout << "Combinations:" << endl;
    for (const auto& c : combinations) {
        for (const auto& num : c) {
            cout << num << " ";
        }
        cout << endl;
    }

    return 0;
}

Permutations:
1 2 3 
1 3 2 
2 1 3 
2 3 1 
3 1 2 
3 2 1 
Combinations:
1 
2 
3 
1 2 
1 3 
2 3