生成可重集的排列

#include <iostream>#include <algorithm>using namespace std;int n, a[1010], p[1010];bool cmp(int a, int b){    return a < b;}void print_permutation(int cur){   //cur 表示当前确定的元素位置;    if(cur == n){        for(int i = 0; i < n-1; ++i){            cout << a[i] << ' ';        }        cout << a[n-1] << endl;    }    else{        for(int i = 0; i < n; ++i){            if(!i || p[i] != p[i-1]){  //枚举的i应该不重复，不遗漏的取遍所有的p[i]值;                int c1 = 0, c2 = 0;                for(int j = 0; j < n; ++j){                    if(p[j] == p[i])  //p数组中p[i]出现的次数;                        ++c1;                }                for(int j = 0; j < cur; ++j){                    if(a[j] == p[i])  //a数组中p[i]目前出现的次数;                        ++c2;                }                if(c2 < c1){                    a[cur] = p[i];                    print_permutation(cur+1);                }            }        }    }}int main(){    int count(0), a;    while(cin >> a){        p[count++] = a;    }    n = count;    sort(p, p+n, cmp);    print_permutation(0);}