C++——函数的调用

时间:2022-02-16 06:43:22

调用前先声明函数:

  >>若函数定义在调用点之前,则无需另外声明

  >>若函数定义在调用点之后,则需要在调用函数前按如下形式声明函数原型(原型声明)

  类型标识符   被调用函数名(含类型说明的形参表)

调用形式

  函数名(实参列表)

嵌套调用

  在一个函数的函数体中。可以调用另一函数,称为嵌套调用

递归调用:

  函数直接或间接调用自身

例一:编写一个求x的n次方的函数

#include<iostream>
using namespace std;

double power(double x, int n)
{
double val = 1.0;
while (n--)
val
*= x;
return val;
}

int main()
{
cout
<< "5 to the power 2 is "<<power(5,2) << endl;
system(
"pause");
return 0;
}

输出结果为25

例二:数制转换:

  输入一个8位二进制数,将其转化为十进制数输出。

#include<iostream>
using namespace std;

double power(double x, int n);//计算x的n次方

int main()
{
int value = 0;
cout
<< "Enter an 8 bit binary number ";
for (int i = 7; i >= 0; i--)
{
char ch;
cin
>> ch;
if (ch == '1')
value
+= static_cast<int>(power(2, i));
}
cout
<< "Decimal value is " << value << endl;
system(
"pause");
return 0;
}

double power(double x, int n)
{
double val = 1.0;
while (n--)
val
*= x;
return val;
}

输出结果:

C++——函数的调用

例三:编写程序求π的值

 π = 16arctan(1/5)-4arctan(1/239)

arctanx = x - x3/3 + x5/5 - x7/7直到级数某项绝对值不大于10-15为止,π和x均为double型

#include<iostream>
using namespace std;

double arctan(double x)
{
double sqr = x * x;
double e = x;
double r = 0;
int i = 1;
while (e / i > 1e-15)
{
double f = e / i;
r
= (i % 4 == 1) ? r + f : r - f;
e
= e * sqr;
i
+= 2;
}
return r;
}

int main()
{
double a = 16.0 * arctan(1 / 5.0);
double b = 4.0 * arctan(1 / 239.0);
cout
<< "PI = " << a - b << endl;
return 0;
}#include
<iostream>
using namespace std;

double arctan(double x)
{
double sqr = x * x;
double e = x;
double r = 0;
int i = 1;
while (e / i > 1e-15)
{
double f = e / i;
r
= (i % 4 == 1) ? r + f : r - f;
e
= e * sqr;
i
+= 2;
}
return r;
}

int main()
{
double a = 16.0 * arctan(1 / 5.0);
double b = 4.0 * arctan(1 / 239.0);
cout
<< "PI = " << a - b << endl;
return 0;
}

输出结果为3.14159

例四:

寻找并输出11-999之间的数m,他满足m,m2,m3都是回文数

#include<iostream>
using namespace std;

bool symm(unsigned n)
{
unsigned i
= n;
unsigned m
= 0;
while (i > 0)
{
m
= m * 10 + i % 10;
i
/= 10;
}
return m == n;
}

int main()
{
for(unsigned m = 11;m<1000;m++)
if (symm(m) && symm(m*m) && symm(m*m*m))
{
cout
<< "m =" << m;
cout
<< "m * m =" << m * m;
cout
<< "m * m * m =" << m * m * m << endl;
}
system(
"pause");
return 0;
}

输出结果:

C++——函数的调用

例五:

C++——函数的调用

#include<iostream>
#include
<cmath>
using namespace std;

const double TINY_VALUE = 1e-10;

double tsin(double x)
{
double g = 0;
double t = x;
int n = 1;
do
{
g
+= t;
n
++;
t
= -t * x * x / (2 * n - 1) / (2 * n - 2);
}
while (fabs(t) >= TINY_VALUE);
return g;
}

int main()
{
double k, r, s;
cout
<< "r =";
cin
>> r;
cout
<< "s =";
cin
>> s;
if (r * r <= s * s)
k
= sqrt(tsin(r)*tsin(r) + tsin(s)*tsin(s));
else
k
= tsin(r * s) / 2;
cout
<< k << endl;
system(
"pause");
return 0;
}

输出结果:

C++——函数的调用

嵌套调用

C++——函数的调用

嵌套调用举例:

输入两个整数,求平方和:

#include<iostream>
using namespace std;

int fun2(int m)
{
return m * m;
}

int fun1(int x, int y)
{
return fun2(x) + fun2(y);
}

int main()
{
int a, b;
cout
<< "Please enter two integers(a and b): ";
cin
>> a >> b;
cout
<< "The sum of square of a nad b: " << fun1(a, b) << endl;
system(
"pause");
return 0;
}

C++——函数的调用

递归调用:

函数直接或间接地调用自身,称为递归调用、

递归过程的两个阶段:

C++——函数的调用

递归调用举例:

求n!

#include<iostream>
using namespace std;

unsigned fac(
int n)
{
unsigned f;
if (n == 0)
f
= 1;
else
f
= fac(n - 1) * n;
return f;
}

int main()
{
unsigned n;
cout
<< "Enter a positive integer: ";
cin
>> n;
unsigned y
= fac(n);
cout
<< n << "!=" << y << endl;
system(
"pause");
return 0;
}

C++——函数的调用

阶乘问题与或图

 C++——函数的调用

举例如下:

用递归发计算从n个人中选择k个人组成一个委员会的不同 组合数

  分析:

    >>由n个人里选k个人的组合数

    = 由n-1个人里选k个人的组合数 + 由m-1个人里选k-1个人的组合数

    当n = k 或k = 0时,组合数为1

  

#include<iostream>
using namespace std;

int comm(int n, int k)
{
if (k > n)
return 0;
else if (n == k || k == 0)
return 1;
else
return comm(n - 1, k) + comm(n - 1, k - 1);
}

int main()
{
int n, k;
cout
<< "Please enter two integers n and k: ";
cin
>> n >> k;
cout
<< "C(n,k) = " << comm(n,k) << endl;
system(
"pause");
return 0;
}

输出结果:

C++——函数的调用