# Mainpage

回傳型態 函式名稱 (引數)
{
函式內容
}

int add(int a, int b)
{
    return a+b
}

#include<iostream>
using namespace std;
int add(int, int);
int sub(int, int);
int mul(int, int);

int main()
{
    char oper;
    int num1, num2;
    cout << "Please enter the operator" << endl;
    cin >> oper;
    cout << "Please enter the first number" << endl;
    cin >> num1;
    cout << "Please enter the second number" << endl;
    cin >> num2;


    switch(oper)
    {
        case '+':
            cout << "Your final answer is:" << endl;
            cout << add(num1,num2);
            break;
        case '-':
            cout << "Your final answer is:" << endl;
            cout << min(num1,num2);
            break;
        case '*':
            cout << "Your final answer is:" << endl;
            cout << mul(num1,num2);
            break;
        default:
            cout << "Invalid operator" << endl;
            break;
    }
}

int add(int a, int b)
{
    return a+b;
}

int sub(int a, int b)
{
    return a-b;
}

int mul(int a, int b)
{
    return a*b;
}

#include<iostream>
using namespace std;
int main()
{
    int lower;
    int upper;
    int temp = 0;
    cout << "Please enter your lower and upper bound" << endl;
    cin >> lower;
    cin >> upper;

    for(int i=lower; i<=upper; i++)
    {
        temp = temp + i;
    }

    cout << "The sum from the number" << " " << lower << " " << "to the number" << " " << upper << " "<< "is" << " " << temp;

    return 0;
}
    

#include<iostream>
using namespace std;
int main()
{
    int upper;
    int i;
    int sum=0;
    cout << "please enter your upper bound" << endl;
    cin >> upper;
    for(i=0; i<=upper; i++)
    {
    sum=sum+i;
    }
    cout << "1+2+3+....+" << upper << " = " << sum;
    return 0;
}

#include<iostream>
using namespace std;
int Z;
int main()
{
int X=10;
int Y=X*X;
Z = Y*Y;
cout << "X = " << X <<", Y = " << Y << " Z = " << Z <<endl;
}

#include<iostream>
using namespace std;

double volume(int); //自訂函式雛形宣告
double surface(int); //自訂函式雛形宣告
const double pi = 3.14159; //宣告全域常數pi，所以函式都可以使用此常數

int main()
{
    int r;
    cout << "please enter the radius"<<endl;
    cin >> r;
    cout << "volume =" << volume(r) << " surface = " << surface(r) << endl;
    return 0;
}

double volume(int r)
{
return (pi*r*r*r*4)/3;
}

double surface(int r)
{
return 4*pi*r*r;
}

//file1.cpp
#include <iostream>
#include "file2.cpp"//使用雙引號將file2涵括進來
using namespace std;
extern void f(int);
int a; //宣告全域變數a
int main(void)
{
    f(5);//呼叫函式f，將回傳值存進a
    cout << "a=" << a <<endl;
    return 0;
}


//file2.cpp
extern int a;
void f (int b)
{
    a=b*b;
    return;
}

#include <iostream>
using namespace std;
int factorial(int n); //宣告自訂函式
int main()
{
    int n;
    cout << "Please enter a number" <<endl;
    cin >> n;
    cout << "The final result is " << factorial(n);
    return 0;
}

int factorial(int n)
{
    if(n==1)
    {
        return 1;
    }
    else
    {
        return n*factorial(n-1); //這行敘述會在呼叫factorial一次
    }
}

#include <iostream>
using namespace std;
int main()
{
    int i, n;
    int temp = 1;
    cout << "Input a number:";
    cin >> n;
    for(i=1; i<=n; i++)
    {
        temp = temp * i;
    }
    cout << temp;
return 0;
}

#include <iostream>
using namespace std;
int main(int argc, char *argv[])
{
    int i;
    cout<<"argc = " <<argc<<endl;
    for(i=0;i<argc;i++)
        cout<<argv[i]<<endl;

    return 0;
}

#include<iostream>
#include<cstdlib>
#include<ctime>
using namespace std;
void game(int, int, int);
int main()
{
    int answer;
    srand(time(NULL));
    answer = rand()%10000;

    int left=1;
    int right=10000;
    int guess;


    cout << "Please take a guess:"<<endl;
    cin >> guess;
    cout << "answer:"<<answer<<endl;

    while(true)
    {
        if(answer<guess)
        {
            right = guess;
            cout<< "Range = "<<left <<" to "<< right<<endl;
        }
        else if(answer>guess)
        {
            left = guess;
         cout<< "Range = "<<left<<" to "<< right<<endl;
        }
        else if(answer==guess)
        {
            cout<< "You are right";
            break;
        }

        cout << "Please take a guess:"<<endl;
        cin >> guess;
    }
    return 0;
}

#include<iostream>
using namespace std;
int C(int, int);
int main()
{
    int n, r;
    cout << "Calculate C(n, r), Please enter number of n and r"<< endl;
    cin >> n >> r;
    cout << C(n,r) <<endl;
    return 0;
}


int C(int n, int r)
{
    if(n < r || r < 0 || n < 0)
        return -1;
    else if(n == r || r == 0)
        return 1;
    else
        return C(n-1,r) + C(n-1, r-1);
}

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