Implementation of recursive algorithms C ++ and PHP for data structures and algorithms

Recursive algorithms of Data Structures and Algorithms C ++ and PHP implement recursive algorithms: they call their own algorithms directly or indirectly.

Implementation process: you can use a function or sub-process to complete recursive operations by directly or indirectly calling the code in a function or sub-process. (For a problem of the same category, the problem is converted into a subproblem of scale-down to a minimum problem with known conditions. then, the problem is solved and the result is returned step by step. It is actually a loop .)

Major manifestation: a small amount of code solves very complicated problems

Features:

1. recursion is to call itself in a method.

2. there must be a clear recursive termination condition called the recursive exit.

3. simple but inefficient, and generally not recommended

4. The return points and local variables of each layer are stored in stacks. Excessive recursion may cause stack overflow.

Instance 1: Factorial

C ++ code:

# Include
 
  
Int factorial (int n); int main () {using namespace std; int n; cout <"enter a number:"; cin> n; cout <n <"factorial:" <factorial (n) <
    
   
Running result:
  
   
      
  
  
   
Instance 2: numeric conversion
  
   
      
  
  
   
Code:
  
   
# Include
    
     
# Include
     
      
Void feelTheBase (char * s, int n, int sys); int main () {using namespace std; char s [60]; int n, sys; cout <"enter an integer:"; cin> n; cout <"Enter the hexadecimal type (, 16) to be converted ):"; cin> sys; feelTheBase (s, n, sys); cout <n <"converted to" <sys <"hexadecimal result:" <s <
        
       
Running result:
  
       
      
  
  
       
   
  
  
       
Example 3: list all subdirectories and files in a directory (it is also convenient to use the scandir function)
  
       
PHP implementation code:
  
       
        "; Rec ($ dir. '/'. $ file, $ lev+ 1);} else {echo str_pad ('', $ lev ,"--"). $ file."
";}} Closedir ($ dh) ;}$ dir ="./"; rec ($ dir) ;?>
  
       
Running result: