#include <stdio.h>

#include <inttypes.h>

/**

 * 递归是一种分而治之、将复杂问题转换为简单问题的求解方法。递归算法有以下优缺点：

 * 优点：使用递归编写的程序简洁、结构清晰，程序的正确性很容易证明，不需要了解其具体的细节。

 * 缺点：递归函数在调用过程中，每一层调用都需要保存临时变量和返回地址、传递参数，因此递归

 *       函数的执行效率低。

 */ 

/**

 * 求阶乘

 */ 

int64_t fact(int32_t n);

int32_t main(int32_t argc, char *argv[]) {

  int32_t n;

  printf("please input a int number: ");

  scanf("%d", &n);

  printf("%d!=%d\n", n ,fact(n));

}

int64_t fact(int32_t n) {

  int32_t x;

  int64_t y;

  if (n < ) { //小于0阶乘无意义

    printf("param error!\n");

    return -;

  }

  if ( == n) { //最后一次返回1

    return ;

  } else {

    return n * fact(n - ); //递归求n的阶乘

  }

}

#include <stdio.h>

#include <inttypes.h>

/**

 * 递归求斐波那契数列的n项

 */ 

int32_t fib(int32_t n);

int32_t main(int32_t argc, char *argv[]) {

  int32_t n;

  printf("please input the number: ");

  scanf("%d", &n);

  printf("the %d option value is: %d\n", n, fib(n));

  return ;

}

int32_t fib(int32_t n) {

  if ( == n) return ;

  if ( == n) return ;

  if (n > ) return fib(n - ) + fib(n - );

}

#include <stdio.h>

#include <inttypes.h>

/**

 * 十进制转二进制

 */ 

void dect_tobin(int32_t number);

int32_t main(int32_t argc, char *argv[]) {

  int32_t n;

  printf("please input a int number: ");

  scanf("%d", &n);

  printf("the binary is: ");

  dect_tobin(n);

  printf("\n");

  return ;

}

void dect_tobin(int32_t number) {

  if ( == number) return;

  dect_tobin(number / );

  printf("%d", number % );

}

#include <stdio.h>

#include <inttypes.h>

/**

 * 递归求数组中的最大值

 */ 

int32_t findmax(int32_t array[], int32_t n);

void displayarray(int32_t array[], int32_t length);

int32_t main(int32_t argc, char *argv[]) {

  int32_t array[] = {, , , , , , , , };

  int32_t length, i;

  length = sizeof(array) / sizeof(array[]);

  displayarray(array, length);

  printf("the max value in array is: %d\n", findmax(array, length));

  return ;

}

int32_t findmax(int32_t array[], int32_t n) {

  int32_t m;

  if (n <= ) return array[];

  m = findmax(array, n - );

  return array[n - ] >= m ? array[n - ] : m;

}

void displayarray(int32_t array[], int32_t length) {

  int32_t i;

  for (i = ; i < length; ++i)

    printf("%3d", array[i]);

  printf("\n");

}

#include <stdio.h>

#include <inttypes.h>

/**

 * 求最大公约数

 */ 

int32_t gcd(int32_t m, int32_t n);

int32_t main(int32_t argc, char *argv[]) {

  int32_t m, n;

  printf("please input two int number: ");

  scanf("%d,%d", &m, &n);

  printf("the max common divisor is: %d\n", gcd(m, n));

  return ;

}

int32_t gcd(int32_t m, int32_t n) {

  if (m > n) {

    return gcd(m - n, n);

  } else if (m < n) {

    return gcd(m, n - m);

  } else {

    return m;

  }

}