第四十三课 递归的思想与应用（上）

 1 #include <iostream>
 2 #include <cstring>
 3 #include "DTString.h"
 4 
 5 using namespace std;
 6 using namespace DTLib;
 7 
 8 unsigned int sum(unsigned int n)
 9 {
10     if( n > 1 )
11     {
12         return n + sum(n - 1);
13     }
14     else
15     {
16         return 1;
17     }
18 }
19 
20 int main()
21 {
22     cout << sum(100) << endl;
23 
24     return 0;
25 }

 1 #include <iostream>
 2 #include <cstring>
 3 #include "DTString.h"
 4 
 5 using namespace std;
 6 using namespace DTLib;
 7 
 8 unsigned int sum(unsigned int n)
 9 {
10     if( n > 1 )
11     {
12         return n + sum(n - 1);
13     }
14     else
15     {
16         return 1;
17     }
18 }
19 
20 unsigned int fac(unsigned int n)
21 {
22     if( n > 2 )
23     {
24         return fac(n - 1) + fac(n - 2);
25     }
26 
27     if( (n == 2) || (n == 1) )
28     {
29         return 1;
30     }
31 
32     return 0;
33 }
34 
35 int main()
36 {
37     cout << sum(100) << endl;
38 
39     for(int i = 1; i <= 10; i++)
40     {
41         cout << i << " : " << fac(i) << endl;
42     }
43 
44     return 0;
45 }

 1 #include <iostream>
 2 #include <cstring>
 3 #include "DTString.h"
 4 
 5 using namespace std;
 6 using namespace DTLib;
 7 
 8 unsigned int sum(unsigned int n)
 9 {
10     if( n > 1 )
11     {
12         return n + sum(n - 1);
13     }
14     else
15     {
16         return 1;
17     }
18 }
19 
20 unsigned int fac(unsigned int n)
21 {
22     if( n > 2 )
23     {
24         return fac(n - 1) + fac(n - 2);
25     }
26 
27     if( (n == 2) || (n == 1) )
28     {
29         return 1;
30     }
31 
32     return 0;
33 }
34 
35 unsigned int _strlen_(const char* s)
36 {
37     if( *s != '