C Language: Recursive small examples

Recursive definition:

a a process or function there is a way to invoke itself directly or indirectly in its definition or description.

Recursive conditions:

(1) recursion is the invocation of itself in a process or function ;

(2) When using a recursive strategy, there must be a definite recursive end condition called a recursive exit.

The use of recursion can simplify the program and reduce code writing, see the example below.

1. Obtain each digit of the decimal number and output it as a character.

#include <stdio.h>

#include <stdlib.h>

void binary_to_ascii (unsigned int value)

{

int num = value% 10; Modulo 10 can get every bit of decimal number

if (value> 9)//recursive end condition

Binary_to_ascii (VALUE/10); Remove the last one, recursively call itself

printf ("%c", num + ' 0 '); The corresponding character is obtained after adding the ASCII value of the character 0

}

int main ()

{

BINARY_TO_ASCII (1234);

System ("pause");

return 0;

}

2. Do not use temporary variables to get string lengths, using Recursive functions

#include <stdio.h>

int my_strlen1 (const char *STR)//How to use temporary variables

{

int count = 0;

while (*STR)

{

count++;

str++;

}

}

int My_strlen (char *str)//using Recursive functions

{

if (*str = = ')//Determine if the string is empty

return 0;

Else

Return 1 + my_strlen (str+1); Pointer to string plus 1 return value plus 1

}//NOTE: Str+1 here cannot be replaced with str++ or ++STR

int main ()//The former pointer will always point to the same character before it is combined

{//The latter, although it is possible to implement the pointer backwards by 1, but

Char *p = "Bit-tech"; has side effects, it changes the contents of the pointer

printf ("%d\n", My_strlen (p));

System ("pause");

return 0;

}

3. Write a recursive function digitsum (n), enter a non-negative integer, return the sum of the numbers that make up it, for example, call Digitsum (1729), then you should return 1+7+2+9, which is 19

#include <stdio.h>

int digitsum (int num) {

int sum = 0;

int tmp = num% 10;

if (num > 0)

sum = Tmp+digitsum (NUM/10);

return sum;

}

int main () {

int num = 0;

printf ("Please enter a non-negative integer \ n");

scanf_s ("%d", &num);

int ret = digitsum (num);

printf ("%d\n", ret);

return 0;

}

4. Write a function implementation n^k, using recursive implementation

#include <stdio.h>

int calculate (int num, int k) {

if (k = = 0)//index is 0

return 1;

The Else//index is not 0

Return num * calculate (num, k-1);//Calculate the power of K, recursively call k-1 times

}

int main () {

int num = 0;

int k = 0;

printf ("Please enter the number and power you want to calculate \ n");

scanf_s ("%d%d", &num, &k);

printf ("%d\n", Calculate (num, k));

return 0;

}

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C Language: Recursive small examples