谭浩强C++习题答案

目录

第三章：

习题3.2

习题3.4

习题3.11

习题3.12

习题3.14

习题3.15

习题3.16

习题3.17

习题3.18

习题3.19

习题3.20

习题3.21

习题3.22

习题3.23

习题3.24

习题3.25

第四章：

习题4.1

习题4.2

习题4.3

习题4.4

习题4.5

习题4.6

习题4.7

第五章：

习题5.1

习题5.3

习题5.4

习题5.7

---

第三章：

习题3.2

#include<iostream>
#include<cmath>
using namespace std;
int main()
{
	double r ;
	double h ;
	double YZC,YMJ, YQB, YQT, YZT;
	cout << "请输入半径r=" << endl;
	cin >> r;
	cout << "请输入高h=" << endl;
	cin >> h;
	YZC = 2 * 3.14 * r;
	YMJ = 3.14 * r*r;
	YQB =4*3.14*r*r ;
	YQT = 3.14 * pow(r,3);
	YZT = YMJ * h;
	cout << "圆周长为：" << YZC << endl; 
	cout << "圆面积为：" << YMJ << endl;
	cout << "圆球面积为：" << YQB<< endl;
	cout << "圆球体积为：" << YQT << endl;
	cout << "圆柱体体积为：" << YZT<< endl;
	return 0;
}

习题3.4

#include<iostream>
using namespace std;
int main()
{
	char c1, c2;
	c1 = getchar();
	c2 = getchar();
	cout << "c1的值为：" << c1 << endl << "c2的值为：";
	putchar(c2);	
	return 0;
}

习题3.11

#include<iostream>
using namespace std;
int main()
{
	int score;
	cout << "请输入您的成绩：";
	cin >> score;
	if (score < 60)
	{
		cout << "您的等级为E" << endl;
	}
	else
	{
		int level;
		level = score / 10;
		switch (level)
		{
		case 9:cout << "您的成绩为A级" << endl; break;
		case 8:cout << "您的成绩为B级" << endl; break;
		case 7:cout << "您的成绩为C级" << endl; break;
		case 6:cout << "您的成绩为D级" << endl; break;
		default:cout<< "您的成绩为A级" << endl; break;
		}
	}
	system("pause");
	return 0;
}

习题3.12

//重点领会：
//printf相对于cout的诸多便利
//定义dayin函数时的思想，特别要分清楚各个参数的作用和目的
#include<iostream>
using namespace std;
int weishu(int n);//位数函数
void dayin(int n);//逐位打印函数
void nixu(int n);//逆序打印函数
int main()
{
	int number=0;
	cout<< "请输入一个不多于5位的正整数:";
	cin >> number;
	weishu(number);
	dayin(number);
	nixu(number);
	return 0;
}
//位数函数
int weishu(int n)
{
	int i = 0;
	for (;n!=0;i++)
	{
		n = n / 10;	
	}
	printf("这是一个%d位数\n", i);
	return i;
}//返回一个位数i方便下面的函数使用
//打印函数
void dayin(int n)
{
	int i = weishu(n);//调用的函数并没有改变外部参数的值，下面可以继续使用n
	int r;
	for (; i > 0; i--)
	{
		r = n % 10;//最后一位的数
		n = n/ 10;
		printf("第%d位上的数是%d\n", i, r);
	}
}
//逆序打印函数
void nixu(int n)
{
	int i = weishu(n);//调用的函数并没有改变外部参数的值，下面可以继续使用n
	int r;
	for (; i > 0; i--)
	{
		r = n % 10;//最后一位的数
		n = n / 10;
		printf("%d   ", r);
	}
}

习题3.14

#include<iostream>
using namespace std;
int main()
{
	cout << "请输入四个整数";
	int a[4];
	int i, s, r;
	for (int s = 0; s < 4; s++)
	{
		cin >> a[s];
	}//将数据放入数组，便于依次对数据操作
	for (int i = 1; i < 4; i++)//控制排序的次数
	{
		for (int r = 0; r < 4 - i; r++)//控制首个数字的排序操作
		{
			int temp;
			if (a[r] > a[r + 1])
			{
				temp = a[r];
				a[r] = a[r + 1];
				a[r + 1] = temp;
			}
		}
	}//冒泡排序
		for (i = 0; i < 4; i++)
			cout << a[i] << "  ";
	return 0;
}

习题3.15

#include<iostream>
using namespace std;
int main()
{
	int m, n;
	cout << "请输入m和n的值：";
	cin >> m >> n;
	int temp = 0;
	temp = (m < n) ? m : n;//将a，b中较小的一个赋给temp
	while (temp > 0)
	{
		if ((m % temp == 0) && (n % temp == 0))
			break;
		--temp;
	}//穷举法
	cout << "最大公因数为："<<temp;
	temp = m * n / temp;//最大公约数*最小公倍数=两数的乘积
	cout << "最小公倍数为：" << temp;
	return 0;
}

习题3.16

#include<iostream>
#include<string>
using namespace std;
int main()
{
	int a, b, c, d;
	char ch;
	cout << "请输入一个字符串：";
	a = b = c = d= 0;
	while ((ch = getchar()) != '\n')//当输入回车的时候（统计完毕）跳出while打印结果
	{
		if (ch >= '0' && ch <= '9')
			a++;//数字
		else if ((ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z'))
			b++;//字母
		else if (ch == ' ')
			c++;//空格
		else
			d++;//其他字符
	}
	cout << "数字，字母，空格和其他字符的个数分别为：" << a <<"," << b<<"," << c<<"," <<d<<"," << endl;
	system("pause");
	return 0;
}

习题3.17

#include<iostream>
#include<cmath>
using namespace std;
int main()
{
	int a, n, x, sn=0;
	cout << "请输入a与n：" << endl;
	cin >> a >> n;
	for (int i = 1; i <=n; i++)
	{
		x = pow(a, i);
		sn += x;//即sn=sn+x;
	}
	cout << "a的阶乘为：" << sn << endl;
	system("pause");
	return 0;
}

习题3.18

#include<iostream>
using namespace std;
int main()
{
	int n;
	cout << "请输入n：";
	cin >> n;
	int Sn=0;
	int temp = 1;
	for (int i = 1; i <= n; ++i)
	{
		temp *= i;
		Sn += temp;
	}
	cout << "n的阶乘为：" << Sn << endl;
	system("pause");
	return 0;
}

习题3.19

#include<iostream>
using namespace std;
int main()
{
	int num = 100;
	int a = 0;//个位
	int b = 0;//十位
	int c = 0;//百位
	do{
		a = num % 10;//获取个位
		b = num / 10 % 10;//获取十位
		c = num / 100;//获取百位
        if (a*a*a+b*b*b+c*c*c==num)//是水仙花数才打印
		{
			cout << num << endl;
		}
		num++;
		}while (num < 1000);
	system("pause");
	return 0;
}

习题3.20

#include<iostream>
using namespace std;
int main()
{
	int lim = 0;
	cout << "请输入一个上限：";
	cin >> lim;
	cout << lim <<"以内的完数有：" << endl;
	//若Sn定义在循环之外，下一次循环会在上一次所得的Sn值为起始，故没出现Sn==a的情况
	for (int a=1; a <= lim; a++)
	{
		int Sn = 0;//在循环内定义变量可以起到重置的作用
		for (int temp = 1;temp<a; temp++)
		{
			if (a%temp==0)
				Sn += temp;
		}
		if (Sn == a)
			cout << a << "  ";
	}
	system("pause");
	return 0;
}

习题3.21

#include<iostream>
using namespace std;
int main()
{
	int num1 = 1;//两个int型变量计算的结果默认是int型
	double num2 = 2;//如果要获取double型的结果，两个计算数必须有一个是double类型
	int lim = 0;
	double an = 0;//单项
	double temp = 0;//临时变量
	double Sn = 0;//单项和
	cout << "请输入项数：";
	cin >> lim;
	for (int i=1;i<lim;i++)
	{
		temp = num2;
		num2 = num1 + num2;
		num1 = temp;
		an = num2 / num1;
		Sn += an;
	}
	printf("%0.2lf", Sn);
	system("pause");
	return 0;
}

习题3.22

#include<iostream>
using namespace std;
int main()
{
	double p = 1;
	for (int i=0;i<9;i++)
	{
		p = (p + 1) * 2;
	}
	cout << "猴子第一天摘了：" << p << "个桃子" << endl;
	system("pause");
	return 0;
}

习题3.23

//用迭代法求x=根号a，求平方根的迭代公式为X(n+1)=1/2（X(n)+a/Xn)
//要求前后两次求出的x的差的绝对值小于10^(-5)
#include<iostream>
using namespace std;
int main()
{
	float a;
	cout << "请输入a的值;";
		cin >> a;
		float m, n;
		m = a / 2;
		while (1)
		{
			n = m;
			m = 0.5 * (m + a / m);
			if (fabs(m - n) < pow(10, -5)) break;
		}
		cout << m << endl;
	system("pause");
	return 0;
}

习题3.24

#include<iostream>
using namespace std;
int main()
{
	for (int i = 1; i <=7; i+=2)
	{
		for (int n = 0; n < i; n++)
			cout << "* ";
		cout << endl;
	}
	for (int i = 5; i >=1; i -= 2)
	{
		for (int n = 0; n < i; n++)
			cout << "* ";
		cout << endl;
	}
	system("pause");
	return 0;
}

习题3.25

#include<iostream>
using namespace std;
int main()
{
	char i, j, k;
	for (i = 'X'; i <= 'Z'; j++)//i，j，k分别为A，B，C的对手
	{
		for (j = 'X'; j <= 'Z'; j++)
		{
			if (i != j)//比赛队员不能重复比赛
			{
				for (k = 'X'; k <= 'Z'; k++)
				{
					if (i != k && j != k)
					{
						if (i != 'X' && k != 'X' && k != 'Z')
						{
							cout << "A的对手是：" << i << endl;
							cout << "B的对手是：" << j << endl;
							cout << "C的对手是：" << k << endl;
						}
					}
				}
			}
		}
	}
	system("pause");
	return 0;
}

第四章：

习题4.1

#include<iostream>
using namespace std;
int main()
{
	int a, b;
	cout << "请输入两个数：" << endl;
	cin >> a >> b;
	//最大公因数
	int num1,num2 = 0;
	if (a >= b)
		num1 = b;
	else
		num1 = a;//将较小数赋值给num1
	for (; a % num1 != 0 || b % num1 != 0 ;)
	{
		num1--;
	}
		cout << "最大公因数为：" << num1 << endl;
	//最小公倍数
	if (a <= b)
		num2 = b;
	else
		num2 = a;//将较大数赋值给num1
	for (;num2%a!=0||num2%b!=0;)
	{
		num2++;
	}
	cout << "最小公倍数为：" << num2 << endl;
	system("pause");
	return 0;
}

习题4.2

#include<iostream>
#include <math.h>
using namespace std;
int main()
{
	double a, b, c, x1, x2;
	cout << "请输入a，b，c的值：" << endl;
	cin >> a >> b >> c;
	if (b * b - 4 * c > 0)
	{
		x1 = b/-2*a + sqrt(b * b - 4 * a * c)/-2*a;//sqrt开平方函数
		x2 = b/-2*a - sqrt(b * b - 4 * a * c)/-2*a;
		cout << "方程的根为：" << x1 <<"," << x2;
	}
	else
	if (b * b - 4 * c < 0)
	{
		cout << "无实数根";
	}
	else
	if (b* b - 4 * c == 0)
	{
		x2 = x1 = b/-2*a + sqrt(b * b - 4 * a * c)/-2*a;
		cout << "方程的根为：" << x1 << "," << x2;
	}
	system("pause");
	return 0;
}

习题4.3

#include<iostream>
using namespace std;
int main()
{
	int n = 0;
	int i = 2;
	cout << "请输入一个整数：" << endl;
	cin >> n;
	if (n <= 0)
	{
		cout << "请重新输入一个正数" << endl;
		cin >> n;
	}
	while(n%i!=0)
	{
		i++;
	}
	if (i == n)
		cout << "这个数是素数" << endl;
	else 
		cout << "这个数不是素数" << endl;
	system("pause");
	return 0;
}

习题4.4

#include<iostream>
int fac(int n);
using namespace std;
int main()
{
	int a, b, c, d;
	cout << "请输入a，b，c的值：" << endl;
	cin >> a >> b >> c;
	d = fac(a) + fac(b) + fac(c);
	cout << "a，b，c的阶乘之和为：" << d << endl;
	system("pause");
	return 0;
}
int fac(int n)
{
	int temp=1;
	for (int i = 1; i <= n; i++)
	{
		temp *= i;
	}
	return temp;
}

习题4.5

#include<iostream>
#include<math.h>
using namespace std;
double ex(int i);
int main()
{
	double sinh = 0;
	int x ;
	cout << "请输入x的值：";
	cin >> x;
	sinh =(ex(x)-1/ex(x))/2;
	cout << "目标函数的值为：" << sinh << endl;
	system("pause");
	return 0;
}
double ex(int i)
{
	double n = 0;
	double e = 2.71;
	n = pow(e, i);
	return n;
}

习题4.6

#include<iostream>
#include<math.h>
double ND(double a, double b, double c, double d);
using namespace std;
int main()
{
	double a, b, c, d;
	cout << "请输入a，b，c，d的值：";
	cin >> a >> b >> c >> d;
	cout << "方程的根的值为：" << ND(a, b, c, d) << endl;
	system("pause");
	return 0;
}
double ND(double a, double b, double c, double d)
{
	double x = 1, x0, f, f1;
	do
	{
		x0 = x;//上次迭代的结果作为下次的x0
		f = ((a * x0 + b) * x0 + c) * x0 + d;
		f1 = (3 * a * x0 + 2 * b) * x0 + c;
		x = x0 - f / f1;
	} while (x - x0 >= 1e-5);
	return x;
}

习题4.7

//找素数时一定要注意2以外的偶数
#include<iostream>
using namespace std;
int prime(int x);
int godbah(int i);
int main()
{
	int i;
	cout << "请输入一个不小于六的偶数：";
	cin >> i;
	while (i % 2 != 0)
	{
		cout << "请重新输入一个不小于六的偶数：";
		cin >> i;
		if (i % 2 == 0)
			break;
	}//保证是一个不小于6的偶数
	godbah(i);
	system("pause");
	return 0;
}
int prime(int x)//判别一个数是否为素数
{
		int n = 2;//传递作用
		if (x == 2)
			return 2;//过滤掉除了2以外的偶数（都不是素数）
		else
			while(x%n!=0)
		    {
				++n;
				if (x == n)
					return x;//注意先后顺序
		    }
}
int godbah(int i)
{
	int n1 = 0;
	int n2 = 0;//接收两个素数
	for (int s = 2; s <= i; ++s)
	{
		n1 = prime(s);//2是素数，从2开始也与prime函数作用契合
		for (int n = 2; n <= i; ++n)
		{
			n2 = prime(n);
			if (n1 + n2 == i)
				break;
		}
		if (n1 + n2 == i)
			break;
	}
	cout << i << "=" <<n1<<"+"<<n2;
		return 0;
}

第五章：

习题5.1

#include<iostream>
using namespace std;
int main()
{
	cout << "100以内的素数有：" << endl;
	for (int i = 1; i < 101; i++)
	{
		int temp = 2;
		while (i % temp != 0&&temp<i)
			++temp;
		if (temp == i)
		{
			cout << i << endl;
		}
	}
	system("pause");
	return 0;
}

习题5.3

#include<iostream>
using namespace std;
int main()
{
	int i = 0;
	int r = 0;
	int temp = 0;
	int arr[3][3] = { {1,2,3},
		              {4,5,6},
		              {7,8,9} };
	for (; i <= 2 && r <= 2; i++, r++)
	{
		temp += arr[i][r];
	}
	for ( i = 2,  r = 2; i >= 0 && r >= 0; i--, r--)
	{
		temp += arr[i][r];
	}
	cout << "该二维数组的对角线元素之和为：" << temp << endl;
	system("pause");
	return 0;
}

习题5.4

#include<iostream>
using namespace std;
int main()
{
	int a = 0;
	int arr[11] = { 1,4,6,7,9,10,12,15,46,47 };
	cout << "请插入一个数：";
	cin >> a;
	for (int i = 0; i < 11; ++i)
	{
		if (arr[i] > a)
		{
			int temp = a;
			a = arr[i];
			arr[i] = temp;
		}//比较完就拿出来，再作为输入的数字进行排序
		else if (a > arr[10])
			arr[10] = a;
	}
	cout << "排序之后：";
	for (int i = 0; i < 11; i++)
		cout << arr[i] << "  ";
	system("pause");
	return 0;
}

习题5.7

//求一个二维数组的鞍点 二维数组可能没有鞍点，如果有，只能有一个 
//鞍点：该元素在行上最大在列上最小
#include<stdio.h>
#include<iostream>
using namespace std;
int main()
{
	int a[4][5];
	int i, j, k, m = 0, n = 0, max = 0, min = 0, temp = 0;
	printf("输入数组的值：\n");
	for (int i = 0; i < 4; i++)
	{
		for (int j = 0; j < 5; j++)
		{
			cin >> a[i][j];
		}
	}
	//for (i = 0; i < 4; i++) 
		//for (j = 0; j < 5; j++)
			//scanf_s("%d", &a[i][j]);//scanf_s解决scanf返回值被忽略的报错
	for (i = 0; i < 4; i++)
	{
		for (j = 0; j < 5; j++)//获得i行最大值 
			if (a[i][m] < a[i][j])
			{
				m = j;
				a[i][m] = a[i][j];
			}
		max = a[i][m];//存储该行最大值                                     
		min = a[0][m];//存储该行最大值所在列的最小值
		for (k = 0; k < 4; k++)
			if (a[k][m] < min)//获得该列最小值 
			{
				min = a[k][m];//从该列第一个元素开始比较,所以上面用数组的方式对min初始化
				n = k;//用n来接收鞍部的列数
			}
		if (max == min) 
		{//若相等则有鞍点，循环结束 
			temp = 1;
			//printf("鞍点为：a[%d][%d]=%d", n, m, a[n][m]);
			cout << "鞍点为：" << "a[" << n << "][" << m << "]" << "=" << a[n][m];
			break;
		}
	}
	if (temp == 0)
		//printf("该二维数组不存在鞍点！");
		cout << "该二维数组不存在鞍点";
}