IT公司100题-1-二叉树转换为双链表

 1 // 21.cc
 2 #include <iostream>
 3 #include <cstring>
 4 using namespace std;
 5 
 6 void print(int* aux, int n) {
 7     for (int i = 0; i < n; i++)
 8         if (aux[i])
 9             cout << i << " ";
10     cout << endl;
11 }
12 
13 void helper(int m, int cur, int* aux, int n) {
14     if (m == 0)
15         print(aux, n);
16     if (m <= 0 || cur == n)
17         return;
18 
19     // 不选cur
20     helper(m, cur + 1, aux, n);
21 
22     // 选cur
23     aux[cur] = 1;
24     helper(m - cur, cur + 1, aux, n);
25     aux[cur] = 0;  // 回溯
26 }
27 
28 void find_combi(int n, int m) {
29     if (n > m) 
30         find_combi(m, m);
31 
32     int* aux = new int[n];  // aux[i] = 1，表示选择i
33     memset(aux, 0, n * sizeof(int));
34     helper(m, 0, aux, n);
35 }
36 
37 int main() {
38     int n, m;
39     cout << "input n and m:" << endl;
40     cin >> n >> m;
41     find_combi(n, m);
42     return 0;
43 }

$ ./a.exe
input n and m:
6 3
1 2
0 1 2
3
1 2
0 3
0 1 2