经典面试题之递归调用几个经典示例

古城微笑少年丶 2022-01-07 00:01 159阅读 0赞

1、 求算1-100

#include <iostream>
    int fun(int n, int &sum)  
    {  
       n && fun(n - 1, sum);  
       return (sum += n);  
    }  
    int main()  
    {  
    int sum = 0;  
    int n = 100;  
    printf("1+2+3+...+n=%d\n", fun(n, sum));  
    return 0;  
    system("pause");
    }

2、 求算  数列 1,1,2,3,5，。。。。第二十个数的 值

#include<iostream>
    using namespace  std;
    
    int  fun(int  n)
    {
    	if(n == 1 || n == 2)
    		return  1;
    	
    	return  (fun(n-1) + fun(n-2));
    }
    
    int  main()
    {
    	int num = 20;
    	printf("num=%d\n",  fun(num));
    	system("pause");
    	return 0;
    }

3、 求文件夹的大小

#include <stdio.h>     
    #include <dirent.h>  
    #include <sys/stat.h>    
    #include <sys/types.h>
    #include <errno.h>
    #include <stdlib.h>
    #include <string.h>
    static int
    mc_get_stat(char *filename, struct stat *stbuf)
    {
        return stat(filename, stbuf);        /* 跟随符号链接 */
    } 
    
    /* 遍历目录或者文件, 返回整个目录或者文件的大小 */
    static blkcnt_t 
    mc_do_du(char *filename, int *len)
    {
        DIR    *dp;
        char    name[256];
        struct     dirent    *p;
        blkcnt_t     n;
        struct stat    stbuf;
        n = 0;
        if(mc_get_stat(filename, &stbuf) == -1){
            fprintf(stderr, "%s cannot access \n", filename);
            return n;
        }	 
        if(S_ISDIR(stbuf.st_mode)){
            dp = opendir(filename);
            while(p = readdir(dp)){
                if(!strcmp(".", p->d_name) || !strcmp("..", p->d_name))
                    continue; 
                else{    /* 文件名超过255个字符时行为未定义 */
                    strcpy(name, filename);
                    strcat(name, "/");
                    strcat(name, p->d_name); 
                    n = mc_do_du(name, len);
                }
            }    
            closedir(dp);    
        }
        return  *len += stbuf.st_size; 
    }    
    
    int main()
    {
      int len =0, len1=0;
       len1 =  mc_do_du("/usr/local/bin/qq", &len);	
    	printf("len1 =%d, len=%d\n", len1, len);
    }