數組排列/全排列(data數組沒有重複元素)

思想:依次生成以data[0]開頭的所有排列,data[1]開頭的所有排列...

1)全排列

#include "iostream"
#include "iterator"
#include "algorithm"
using namespace std;

int data[5] = {1,2,3,4,5};
void perm(int index[],int n, int k) {
    int i;
    if (k == n) {
        for(int i = 0; i < n; i++)
            cout<<data[index[i]]<<" ";
        cout<<endl;
        return;
    }
    for (i = k; i < n; i++) {
        swap(index[k], index[i]);
        perm(index, n, k + 1);
        swap(index[k], index[i]);
    }

}

int main() {
    int index[] = {0,1, 2, 3, 4};
    perm(index, 5, 0);
    return 0;
}

2)排列,n個元素中抽取m個的排列(不保證輸出的順序)

#include "iostream"
#include "iterator"
#include "algorithm"
using namespace std;

int data[5] = {1,2,3,4,5};
void perm(int index[],int n, int m,int k) {
    int i;
    if (k == m) {
        for(int i = 0; i < m; i++)
            cout<<data[index[i]]<<" ";
        cout<<endl;
        return;
    }
    for (i = k; i < n; i++) {
        swap(index[k], index[i]);
        perm(index, n,m, k + 1);
        swap(index[k], index[i]);
    }

}

int main() {
    int index[] = {0,1, 2, 3, 4};
    perm(index, 5, 3,0);
    return 0;
}