1. 请用c语言编写程序，求和：S = 1-(1/2)+(1/3)-(1/4)+…+(1/n)，其中n=10

 #include"stdio.h"

int main(){
	int i = 1;
	int tag = 1;  //表示符号
	double sum = 0;
	while(i<=10){
		sum += tag*(1.0/i);
		i++;
		tag *= -1;
	}
	printf("%f\n",sum);
	return 0;
}

2. 请用C语言编写一个函数fun(char *s)，该函数的功能是：把字符串中的内容逆置。

例如：字符串中原有的字符串有"abcdefg"，则调用该函数后，串的内容改为"gfedcba"。

#include"stdio.h"
#include"stdlib.h"

char* fun(char *s){
	int length = 0;
	char *c = s;
	while(*c != '\0'){
		length++;
		c++;
	}
	
	char *new_s = (char *)malloc(sizeof(char)*length);
	int i=0;
	while(i<length){
		new_s[i] = s[length-i-1];
		i++;
	}
	return new_s;
}

int main(){
	char s[]="abcdefg";
	//char s[20];
	//gets(s);
	char *new_s;
	new_s=fun(s);
	puts(new_s);
	return 0;
}

3. 编写程序从基类派生圆柱，设计成员函数输出它们的面积和体积。

基类定义如下:

class Basic//基类
{
	protected: 
		double r;
	public:
		Basic() { r = 0; }
		Basic(double a){ r = a;}
};

#include <iostream>
#define pi 3.1415926

using namespace std;

class Basic{
	protected:
		double r;
	public:
		Basic(){
			r = 0;	
		}
		Basic(double a){
		 	r = a;	
		}
};
class cylinder:public Basic {//圆柱
	private:
		double h;
	public:
		cylinder(double b,double a){
			r = a;
			h = b;
		}
		double get_area(){  //面积
				return pi*r*r;
		}
		double get_volume(){   //体积
			return get_area()*h;
		}
};

int main()
{
	cylinder c(5,2);
	cout<<c.get_area()<<endl;
	cout<<c.get_volume()<<endl;
   return 0;
}