C++第二章作业

第一题：

/****** 例一 *******/

#include<iostream>
#include<iomanip>
using namespace std;
int main()
{
bool flag = true;
cout<<flag<<endl;
cout<<boolalpha<<flag<<endl;
cout<<flag + 5<<endl;
flag = 0;
cout<<"执行语句flag=0;后flag的值为:"<<boolalpha<<flag<<endl;
flag = 0.0;
cout<<"执行语句flag=0.0;后flag的值为:"<<boolalpha<<flag<<endl;
return 0;
}

/****** 例二 *******/
#include<iostream>
using namespace std;
int main()
{
int a,b,c,d;
a = 4;
b = a;
a = 5;
c = d = 6;
c *= a;
d %= a + b;
cout<<"a = "<<a<<endl
<<"b = "<<b<<endl
<<"c = "<<c<<endl
<<"d = "<<d<<endl;
return 0;
}

/****** 例三 *******/
#include<iostream>
using namespace std;
int main()
{
int i,j,m,n;
i = 1000;
j = 1000;
m = i + j;
n = i * j;
cout<<"m = "<<m<<endl;
cout<<"n = "<<n<<endl;
return 0;
}

/****** 例四 *******/
#include<iostream>
using namespace std;
int main()
{
int i = 6,j,k,temp;
j = ++i;
k = i++;
++i = 1;
cout<<"i = "<<i<<endl
<<"j = "<<i<<endl
<<"k = "<<k<<endl;
return 0;
}

/****** 例五 *******/

#include<iostream>using namespace std;int main(){char ch;cout<<"please input a character: ";cin>>ch;ch = ch>= 'a'&&ch<= 'z'?ch - 'a' + 'A': ch;cout <<"The result is: "<<ch<<endl;return 0;}  

/****** 例六 *******/

#include<iostream>using namespace std;int main(){char ch = 'c';int a,b = 13;float x,y;x = y = 2.0;a = ch + 5;x = b / 2 / x;y = b / y / 2;cout<<"a = "<<a<<endl<<"x = "<<x<<endl<<"y = "<<y<<endl;return 0;}  

/****** 例七 *******/#include<iostream>using namespace std;int main(){int ab,ac;double b = 3.14;char c = 'A';ab = int(b);ac = int(c);cout<<"b = "<<b<<endl<<"ab = "<<ab<<endl<<"c = "<<c<<endl<<"ac = "<<ac<<endl;return 0;}  

第二题：

/****** 计算三角形的面积和周长 *******/#include<iostream>#include<math.h>                       //后面需要使用sqrt()函数计算面积,所以先调用出来using namespace std;int main(){float a,b,c,d,C,S;                 //定义三角形三边a,b,c以及d,C,Scout<<"请输入三角形的三边长度"<<endl;cin>>a>>b>>c;if(a+b>c&&a+c>b&&b+c>a){d=(a+b+c)/2;C=a+b+c;S=sqrt(d*(d-a)*(d-b)*(d-c));cout<<"该三角形的周长为:"<<C<<endl;cout<<"该三角形的面积为:"<<S<<endl;}else{cout<<"您所输入的三条边的长度无法组成三角形,重新运行程序"<<endl;}return 0;}

第三题：

/******习题三A*****/#include <iostream>#include <math.h>                             //数学函数调用头文件<math.h>using namespace std;int main(){int e = 1, f = 4, g = 2;float m = 10.5, n = 4.0, k;k = (e+f)/g+sqrt((double)n)*1.2/g+m;     //n的类型强制转换为doubhle型cout<<"k = "<<k<<endl;return 0;}  

/******习题三B******/#include <iostream>using namespace std;int main(){float x = 2.5, y = 4.7;int a = 7;cout<<x+a%3*(int(x+y)%2)/4<<endl;     //(x+y)强制转换成int类型return 0;}  

第四题：

#include <iostream>#include <math.h>                        //数学函数调用using namespace std;int main(){float a, b, c;                          //定义变量a，b，cdouble x1, x2, k;cout<<"请输入二次项系数: "<<endl;cin>>a;cout<<"请输入一次项系数: "<<endl;cin>>b;cout<<"请输入常数项: "<<endl;cin>>c;

第五题：

/******加密与解密程序******/#include <iostream>using namespace std;int main(){char a[25],b[25],c[25],e[25];          //定义四个一维字符型数量组int k;cout<<"欢迎进行名字加密与解密程序"<<endl;        //加密解密选择cout<<"加密请输入“1”，解密请输入任意数字"<<endl;cin>>k;if(k==1)                                        //加密{int i;cout<<"请输入你要加密的名字"<<endl;         //输入要加密的名字fflush(stdin);                              //清除输入缓存cin>>a;                                     //从键盘获取字符cout<<"该名字的加密成果为："<<endl;         //加密结果输出for(i=0;i<25;i++){if(a[i]==0){break;}b[i]=a[i];b[i]=b[i]+10;                           //加密方法c[i]=b[i];cout<<c[i];}cout<<endl;}else                                           //解密{cout<<"请输入你要解密的名字"<<endl;        //输入要解密的名字fflush(stdin);                             //清除输入缓存cin>>a;cout<<"该名字的解密成果为："<<endl;        //解密结果输出for(int i=0;i<25;i++){if(a[i]==0){break;}b[i]=a[i];b[i]=b[i]-10;                          //解密方法e[i]=b[i];cout<<e[i];}cout<<endl;}return 0;}  

k = b*b-4*a*c; //用一元二次方程的求根公式求出解x1, x2 x1 = (-b+sqrt(k))/(2*a); x2 = (-b-sqrt(k))/(2*a); if(k>=0) //根据k的值不同分类讨论 { if(x1==x2) { cout<<"一元二次方程的解只有1个，x= "<<x1<<endl; } else { cout<<"一元二次方程的解有2个，x1= "<<x1 <<" x2= "<<x2<<endl; } } else { cout<<"一元二次方程有虚根，x1=i* "<<x1//求出一元二次方程的虚根 <<" x2=i* "<<x2<<endl; } return 0; }

（这题其实是看我们学霸的，但还是不会）