C++程序设计第三版（谭浩强）第四章课后习题答案

自己写的做练习，如果有问题多谢指点

4.2

#include "stdafx.h"
#include 
#include 
#include
using namespace std;
void delta1(float, float);
void delta2(float, float);
void delta3(float, float);
float delta;
int main()
{
	float a, b, c;
	cout << "Please input three numbers:" << endl;
	scanf_s("%f %f %f", &a, &b, &c);
	delta = b * b - 4 * a*c;
	if (delta > 0)
		delta1(a, b);
	else if (delta == 0)
		delta2(a, b);
	else if (delta < 0)
		delta3(a, b);
	return 0;
}
void delta1(float a, float b)
{
	float x1, x2;
	x1 = (-b + sqrt(delta)) / (2 * a);
	x2 = (-b - sqrt(delta)) / (2 * a);
	cout << "x1=" << x1 << " x2=" << x2;
}
void delta2(float a, float b)
{
	float x;
	x = (-b) / (2 * a);
	cout << "x1=x2=" << x;
}
void delta3(float a, float b)
{
	float xb, sb;
	sb = (-b) / (2 * a);
	xb = (sqrt(-delta)) / (2 * a);
	cout << "x1=" << sb << "+" << xb << "i" << endl;
	cout << "x2=" << sb << "-" << xb << "i" << endl;
}

4.3

#include "stdafx.h"
#include 
#include
using namespace std;

int main()
{
	void prime(int);
	int n;
	cout << "Please input a number:" << endl;
	cin >> n;
	prime(n);
	return 0;
}
void prime(int n)
{
	for (int i = 2; i <= sqrt(n); i++)
		if (n%i == 0)
		{
			cout << "This number isn't a prime number.";
			break;
		}
	cout << "This number is a prime number.";
}

4.4

#include "stdafx.h"
#include 
#include "stdio.h"
#include
using namespace std;

int main()
{
	int fac(int);
	int a, b, c;
	cout << "Please input three numbers:" << endl;
	scanf_s("%d %d %d", &a, &b, &c);
	int x;
	x = fac(a) + fac(b) + fac(c);
	cout << "a!+b!+c!=" << x << endl;
	return 0;
}
int fac(int n)
{
	int x;
	if (n == 0 || n == 1)
		x = 1;
	else x = fac(n - 1)*n;
	return x;
}

4.5

#include "stdafx.h"
#include 
#include "stdio.h"
#include
using namespace std;

int main()
{
	float ex(int);
	float sinh(int);
	int n;
	cout << "Please input x:" << endl;
	cin >> n;
	float x = sinh(n);
	cout << x;
	return 0;
}
float ex(int n)
{
	return (exp(n));
}
float sinh(int n)
{
	float sinh;
	sinh = (ex(n) - ex(-n)) / 2;
	return sinh;
}

4.7

#include "stdafx.h"
#include 
#include "stdio.h"
#include
using namespace std;

int main()
{
	void gotbaha(int);
	cout << "Please input a number:" << endl;
	int n;
	cin >> n;
	gotbaha(n);
	return 0;
}
void gotbaha(int n)
{
	bool prime(int);
	if (n % 2 != 0)
		cout << n << " is not a even number.";
	else
	{
		int a = 3, b = n - 3;
		for(int i=2;i

4.8

#include "stdafx.h"
#include 
#include "stdio.h"
#include
using namespace std;

int main()
{
	int lrd(int, int);
	int n, x;
	cout << "Please input the n and x:" << endl;
	scanf_s("%d %d", &n, &x);
	int y=lrd(n, x);
	cout << "The value is" << y;
	return 0;
}
int lrd(int n,int x)
{
	int f;
	if (n == 0)
		f = 1;
	else if (n == 1)
		f = x;
	else
		f = (2 * n - 1)*x - lrd(n - 1, x) - (n - 1)*lrd(n - 2, x) / n;
	return f;
}

4.9

#include "stdafx.h"
#include 
#include "stdio.h"
#include
using namespace std;

int main()
{
	void hanoi(int, char, char, char);
	char A, B, C;
	cout << "Please input the number" << endl;
	int n;
	scanf_s("%d %c %c %c", &n, &A, 1, &B, 1, &C, 1);
	hanoi(n, A, B, C);
	return 0;
}
void hanoi(int n, char A, char B, char C)
{
	void move(char, char);
	if (n == 1)
		move(A, C);
	else
	{
		hanoi(n - 1, A, C, B);
		move(A, C);
		hanoi(n - 1, B, A, C);
	}
}
void move(char x, char y)
{
	cout << x << " to " << y<

4.10

#include "stdafx.h"
#include 
#include "stdio.h"
#include
using namespace std;

int main()
{
	void exchange(int);
	int n;
	cout << "Please input a number:";
	cin >> n;
	exchange(n);
	return 0;
}
void exchange(int n)
{
	if (n / 10 != 0)
		exchange((int)(n/10));
	cout << (char)(n % 10 + '0');
}

4.11

#include "stdafx.h"
#include 
#include "stdio.h"
#include
using namespace std;

int main()
{
	int sum(int);
	int n;
	cout << "Please input a number:";
	cin >> n;
	int y = sum(n);
	cout << "The value is " << y;

}
int sum(int n)
{
	int f;
	if (n == 1)
		f = 1;
	else
		f = sum(n - 1) + n * n;
	return f;
}

4.12

#include "stdafx.h"
#include 
#include "stdio.h"
#include
#define s(a,b,c) 0.5*((a)+(b)+(c))
#define area(s,a,b,c) sqrt(s*(s-(a))*(s-(b))*(s-(c)))
using namespace std;

int main()
{
	int a, b, c;
	cout << "Please input the length of the three sides of a triangle:";
	scanf_s("%d %d %d", &a, &b, &c);
	cout << "The area of this triangle is " << area(s(a,b,c),a,b,c);
	return 0;
}