1 #include<iostream>
 2 #include<ctime>
 3 using namespace std;
 4 
 5 #define N 4
 6 
 7 void fullarrange(char num[], int len, int index) {
 8     if(index == len) {
 9         cout << num << " ";
10         return;
11     }
12     for(int i = 0; i < 10; i++) {
13         num[index] = ‘0‘ + i;
14         fullarrange(num, len, index+1);
15     }
16 }
17 
18 int main()
19 {
20     char num[N];
21     memset(num, ‘0‘, N);
22     num[N-1] = ‘\0‘;
23     for(int i = 0; i < 10; i++) {
24         num[0] = i + ‘0‘;
25         fullarrange(num, N-1, 1);
26     }
27     return 0;
28 }