C++初学2

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在 C++初学的基础上做了部分修改，并且在Dev-C++中重新编译。

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/*
 * helloworld_1.cpp
 *
 *  Created on: 2014-05-13

 *      Author: xiejiaohui
 */

#include

using namespace std;

int main() {
	cout<<"同学们，你们好！";
	system("PAUSE");
	return 0;
}

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/*
 * helloworld.cpp
 *
 *  Created on: 2014-05-13

 *      Author: xiejiaohui
 */

#include

using namespace std;

int main() {
	cout<<"同学们，你们好！";
	system("PAUSE");
	return 0;
}

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/*
 * helloworld2.cpp
 *
 *  Created on: 2014-05-13

 *      Author: xiejiaohui
 */

#include

using namespace std;

void hello(char *s)
{
	cout << s << ", 你们好!" << endl;
}

int main()
{
	hello("同学们");
	hello("老师们");
	system("PAUSE");
	return 0;
}

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/*
 * area.cpp
 *
 *  Created on: 2014-05-13

 *      Author: xiejiaohui
 */

#include

using namespace std;

#define PI 3.1416

double Area(double r)
{
	return PI * r * r;
}

int main()
{
	double radius, area;
	cout << endl << "请输入圆的半径：";
	cin >> radius;
	area = Area(radius);
	cout << endl << "圆的面积：" << area;
	system("PAUSE");
}

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/*
 * maxValue.cpp
 *
 *  Created on: 2014-05-13

 *      Author: xiejiaohui
 */

#include 

using namespace std;

int MaxValue(int a, int b, int c) {
    if (a < b) a = b;
    if (a < c) a = c;
    return a;
}

int main() {
    int x1 = 5, x2 = 30, x3 = 8;
    cout << "三个数中最大的数为：" << MaxValue(x1, x2, x3);
    system("PAUSE");
    return 0;
}

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/*
 * twoValue.cpp
 *
 *  Created on: 2014-05-13

 *      Author: xiejiaohui
 */

#include 

using namespace std;

int main() {
    int i, j;
    cout << "请输入2个整数：";
    cin >> i >> j;
    cout << "2个数中比较大的数是：";
    if(i >= j)
        cout << i << endl;
    else
        cout << j << endl;
    system("PAUSE");
    return 0;
}

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/*
 * threeValue.cpp
 *
 *  Created on: 2014-05-13

 *      Author: xiejiaohui
 */

#include 

using namespace std;

int main() {
    int i, j, k;
    cout << "请输入3个整数：" << endl;
    cin >> i >> j >> k;
    cout << "3个数中最大的是：";
    if(i >= j) {
        if(i >= k)
            cout << i << endl;
        else
            cout << k << endl;
    } else {
        if(j >= k)
            cout << j << endl;
        else
            cout << k << endl;
    }
    system("PAUSE");
    return 0;
}

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/*
 * threeValue2.cpp
 *
 *  Created on: 2014-05-13

 *      Author: xiejiaohui
 */

#include 

using namespace std;

int main() {
    int i, j, k;
    cout << "请输入3个整数： ";
    cin >> i >> j >> k;
    cout << "3个整数中比较大的整数是：";
    if(i < j) i = j;
    if(i < k) i = k;
    cout << i << endl;
    system("PAUSE");
} 

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/*
 * threeValueSort.cpp
 *
 *  Created on: 2014-05-13

 *      Author: xiejiaohui
 */

// 输入3个数，然后按照从大到小的顺序输出
#include 

using namespace std;

int main() {
    int i, j, k, p;
    cout << "请输入3个整数：";
    cin >> i >> j >> k;
    if (i < j) {
        p = i;
        i = j;
        j = p;
    }
    if (i < k) {
        p = i;
        i = k;
        k = p;
    }
    if (j < k) {
        p = j;
        j = k;
        k = p;
    }
    cout << endl << "三个整数从大到小的排序为：";
    cout << i << ' ' << j << ' ' << k;
    system("PAUSE");
}

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/*
 * scoreLeve.cpp
 *
 *  Created on: 2014-05-13

 *      Author: xiejiaohui
 */

#include 

using namespace std;

/**
 * 输入一个0~100分范围内的成绩，
 * 显示相应的等级
 * 90~100 -优
 * 80~89  -良
 * 70~79  -中
 * 60~69  -及格
 * 60分以下   -不及格
 */

int main() {
    float score;
    cout << "请输入成绩：";
    cin >> score;
    if (score < 0 || score > 100)
        cout << "成绩输入必须在0~100分之间";
    else if (score < 60)
        cout << "不及格" << endl;
    else if (score < 70)
        cout << "及格" << endl;
    else if (score < 80)
        cout << "中" << endl;
    else if (score < 90)
        cout << "良" << endl;
    else
        cout << "优" << endl;
    
    system("PAUSE");
    return 0; 
}

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/*
 * scoreLeve2.cpp
 *
 *  Created on: 2014-05-13

 *      Author: xiejiaohui
 */

/**
 * 输入一个0~100分范围内的一个成绩，显示相应的登记，
 * 但要求用switch多分支结构代替原来的if多分支结构
 */

#include 

using namespace std;

int main() {
    float score;
    cout << "请输入0~100分之间的成绩：";
    cin >> score;
    switch(int(score) / 10) {
        case 0:
        case 1:
        case 2:
        case 3:
        case 4:
        case 5: cout << "不及格" << endl; break;
        case 6: cout << "及格" << endl; break;
        case 7: cout << "中" << endl; break;
        case 8: cout << "良" << endl; break;
        case 9:
        case 10: cout << "优" << endl; break;   
        default: cout << "成绩必须输入在0~100分之间"; 
    }
    system("PAUSE");
    return 0;
}

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/*
 * forTest.cpp
 *
 *  Created on: 2014-05-13

 *      Author: xiejiaohui
 */

#include 

using namespace std;

int main() {
    for (int i = 0; i <= 50; i++)
        cout << i << " ";
    system("PAUSE");
}

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/*
 * forTest2.cpp
 *
 *  Created on: 2014-05-13

 *      Author: xiejiaohui
 */

#include 

using namespace std;

int main() {
    double x, s = 0;
    cout << "请输入10个整数：";
    for (int i = 0; i < 10; i++) {
        cin >> x; 
        s += x;
    }
    cout << "合计：" << s;
    system("PAUSE");
} 

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/*
 * forTest3.cpp
 *
 *  Created on: 2014-05-13

 *      Author: xiejiaohui
 */

/**

用for循环显示一个带 *号的6行的三角形

     *
    ***
   *****
  *******
 *********
***********

行号    空格数    *数
0    5    1
1    4    3
2    3    5
3    2    7
4    1    9
5    0    11
------------
i    5-i    i+i+1

*/

#include 

using namespace std;

int main() {
    for (int i = 0, j = 0; i < 6; i++) {
        for (j = 0; j < 5 - i; j++)
            cout << ' '; // 打印空格
        for ( j = 0; j < i + i + 1; j++)
            cout << '*'; // 打印 *
        cout << endl;
    }
    system("PAUSE");
    return 0;
}

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/*
 * whileTest.cpp
 *
 *  Created on: 2014-05-13

 *      Author: xiejiaohui
 */

/*
求数列：
1/2, 3/4, 5/8, 7/16, 9/32......
的所有大于等于0.000001的数据项之和，
显示输出计算的结果。

方法一：利用通项公式
序号        分子                       分母
1    2*1-1=1    2=2
2    2*2-1=3    2*2=4
3    2*3-1=5    2*2*2=8
4    2*4-1=7    2*2*2*2=16
...  ...        ...
i    2*i-1      2*2*2*...*2

*/

#include 
#include 

using namespace std;

int main() {
    int i = 1;
    double s = 0.0, s0;
    while ((s0 = (i + i - 1) / pow(2, i)) >= 0.000001) {
        s += s0;
        i++;
    }
    cout << s;
    system("PAUSE");
    return 0;
}

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/*
 * whileTest2.cpp
 *
 *  Created on: 2014-05-13

 *      Author: xiejiaohui
 */

/*
求数列：
1/2, 3/4, 5/8, 7/16, 9/32......
的所有大于等于0.000001的数据项之和，
显示输出计算的结果。

方法二：利用递推公式
序号        分子                       分母
1    1          2
2    1+2=3      2*2=4
3    3+2=5      2*4=8
4    5+2=7      2*8=16
...  ...        ...
i    ni         di
i+1  ni+2       2*di

*/

#include 

using namespace std;

int main() {
    int n = 1, d = 2;
    double s = 0.0, s0;
    while ((s0 = double(n) / d) >= 0.000001) {
        s += s0;
        n += 2;
        d += d;
    }
    cout << s;
    system("PAUSE");
    return 0;
}

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/*
 * whileTest3.cpp
 *
 *  Created on: 2014-05-13

 *      Author: xiejiaohui
 */

/*

已知

sinx = x/1 - x*x*x/3*2*1 + x*x*x*x*x/5*4*3*2*1 - x*x*x*x*x*x*x/7*6*5*4*3*2*1 + ......

设计一个程序，输入弧度 x, 通过累加所有绝对值大于等于0.000001

的项来计算 sinx 的近似值，显示计算结果并对照调用标准函数sin的计算结果.

序号          分子                         分母
1       x                                  1!
2       x*(-x*x)=-x*x*x                    1!*2*3=3!
3       (-x*x*x)*(-x*x)=x*x*x*x*x          3!*4*5=5!
4       x*x*x*x*x*(-x*x)=-x*x*x*x*x*x*x    5!*6*7=7!
...     ...                                ...
i       n(i)                               d(i)
i+1     n(i)*(-x*x)                        d(i)*(2*i - 2)(2*i - 1)

*/

#include 
#include 

using namespace std;

int main() {
    const double dPI = 2 * 3.1415926;
    double x;
    cout << "请输入一个弧度值：";
    cin >> x;
    if (x > 0.0)
        while (x > dPI) x -= dPI;
    else
        while (x < -dPI) x += dPI;
    
    double i = 1.0, n = x, d = 1.0, s = 0, s0;
    
    while (fabs(s0 = n / d) >= 0.000001) {
        s += s0;
        i++;
        n *= (-x * x);
        d *= (i + i - 2) * (i + i -1);
    }
    
    cout << "我的程序计算的值为： " << s << endl;
    cout << "sin()函数计算的值为：" << sin(x);
    system("PAUSE");
    return 0;
}

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说明：以上例子来源于中央广播电视大学视频
《c++语言程序设计》 首都经贸大学 李宁 副教授。（现在应该是正教授了）。