C++简单的回溯

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


using namespace std;

const int N = 25;

bool books[N];
int index = 0;
void dfs(vector<vector<int>>&s, vector<int>& v, vector<int>& tmp, int m, int cur)
{
    if (v.size() == m)
    {
        s.push_back(v);
        return;
    }
    for (int i = cur; i < tmp.size(); i++)
    {
        if (i > 0 && tmp[i] == tmp[i - 1] && books[i - 1] == false)
            continue;
        if (books[i] == false)
        {
            books[i] = true;
            v.push_back(tmp[i]);
            dfs(s, v, tmp, m, i + 1);
            v.pop_back();
            books[i] = false;
        }
    }
}

int main()
{
    int n = 0;
    int m = 0;
    cin >> n >> m;
    vector<int> tmp(n);
    for (int i = 0; i < n; i++)
    {
        cin >> tmp[i];
    }
    sort(tmp.begin(), tmp.end());
    vector<vector<int>> s;
    vector<int> v;
    dfs(s, v, tmp, m, 0);
    for (auto e : s)
    {
        for (auto ee : e)
        {
            cout << ee << " ";
        }
        cout << endl;
    }
    system("pause");
}