宣老第三章程序

爱因斯坦阶梯

#include <iostream>
using namespace std;
int  main(void)
{
    int  k = 7;
    while( !((k % 3 == 2) && (k % 5 == 4) && (k % 6 == 5)))
    {
        k+=14;
    }

    cout <<  "k = " <<  k << endl;
    return 0;
}

素数

#include <iostream>
#include <cmath>
using namespace std;
int  main(void)
{
    int  n, j, s;
    for(n = 101; n < 200; n += 2)
    {
        s = (int) sqrt((double)n);
        for(j = 2; j <= s; ++j)
        {
            if(n % j == 0)
            {
                break;
            }
        }
        if(j > s)
        {
            cout << n << endl;
        }
    }
    return 0;
}

倍级数

#include <iostream>
using namespace std;
int main(void)
{
    float s, t;
    int i, a, n;
    do{
        cin >> a >> n;
        if (a < 1 || a > 9)
        {
            cout << "Data Input Error !\nInput again.";
        }
    }while( a < 1 || a > 9);

    s = 0.0f;
    t = a;

    for(i = 1; i <= n; i++)
    {
        s += t; 
        t = t * 10 + a;
    }
    cout << "s = " << s << endl;
    return 0;
}

二分法求根

#include <iostream>
#include <cmath>
using namespace std;
int  main(void)
{
    float x1, x2, x, f1, f2, f;

    cin >> x1 >> x2;

    f1 = x1 * x1 * x1 - 6.0f * x1 - 1.f;        //解析式
    f2 = x2 * x2 * x2 - 6.0f * x2 - 1.f;
    cout << x1 << " " << x2 << " " << f1 << " " << f2 << endl;
    do {
        x = (x1 + x2) / 2.f;        //中点
        f = x * x * x - 6.0f * x - 1.f;
        if(f * f1 >= 0.f)
        {
            f1 = f;
            x1 = x;
        }
        else
        {
            f2 = f;
            x2 = x;
        }
     }while(fabs(x1 - x2) >= 1e-6f);

     cout << "Root is :" <<  (x1 + x2) / 2.f << endl;
     return 0;
}

水仙花数

#include <iostream>

using namespace std;
int  main(void)
{
    int n, a, b, c;
    for(n = 100 ; n <= 999 ; n++)
    {
        a = n / 100;
        b = n % 100 / 10;
        c = n % 10;
        if(a * a * a + b * b * b + c * c * c == n)
        {
            cout << n << "锛氭槸姘翠粰鑺辨暟銆? << endl;
        }
    }
    return 0;
}

一元二次方程求根

#include  <iostream>
#include  <iomanip>
#include  <cmath>
#include  <cstdlib>

using namespace std;

int  main(void){
    float a,b,c,d;

    cout << "璇蜂互绌烘牸鍒嗛殧鎸夐『搴忚緭鍏ヤ竴鍏冧簩娆℃柟绋嬬殑绯绘暟锛?;
    cin >> a >> b >> c;

    d = b * b - 4.0f * a * c;
    if((float)fabs(d) < 1.0e-6f)
    {
        cout << "x1 = x2 = " <<  -b/(2.0f*a) << endl;
    }
    else
    { 
         if(d > 0)
         {
              cout << fixed << setprecision(4);
              cout << " x1=" << (-b + (float)sqrt(d) ) / (2.0f * a) << endl;
              cout << " x2=" << (-b - (float)sqrt(d) ) / (2.0f * a) << endl;
         }
         else     
         {
              cout << fixed << setprecision(4);
              cout << "x1=" << -b/(2.0f*a) << " + i" << (float)sqrt(-d)/(2.0f*a) << endl;
              cout << "x1=" << -b/(2.0f*a) << " - i" << (float)sqrt(-d)/(2.0f*a) << endl;
         }
   }
   system("pause");
   return 0;
}

求pi

/********************************************************************
    created:    2021/09/22
    created:    22:3:2019   9:46
    filename:   PI.CPP
    file path:  D:\CAIWorkSpace\2018~2019第二学期教学文档\CCAI14FIN
    file base:  PI
    file ext:   CPP
    author:     Xuan

    purpose:    本程序用于输入精度并计算圆周率统计计算时间次数。
*********************************************************************/


#include <iostream>
#include <iomanip>
#include <ctime>
#include <cstdlib>
using namespace std;

int main(void)
{
    clock_t start, end;
    double dItem, dPi, dPrecision, dSign;
    long long llCount = 0ll;

    cout << "Input precision: ";
    cin >> dPrecision;

    dItem = 1.0;
    dPi = 0.0;
    dSign = 1.0;

    start = clock();
    do{
        dPi += 1.0 / dItem * dSign;
        dItem += 2.;
        dSign = -dSign;
        llCount++;
    }while(1. / dItem  > dPrecision / 4.);

    end = clock();

    cout << fixed << setprecision(16);
    cout << "PI = " << setw(20) << 4.0 * dPi << endl;
    cout << "Number = " << llCount << endl;
    cout << "Time consuming = " << setprecision(3) <<((float)(end - start) / CLK_TCK) << 's' << endl;

    system("pause");
    return 0;
}

积分

#include <iostream>
using namespace std;
int main(void){
    float a, b, f0, f1, h, x, s = 0.0f;
    int n, i;
    cin >> a >> b >> n;
    h = (b - a) / n;
    x = a;
    f0 = x * x + 12.0f * x + 4.0f;
    for(i = 0; i < n; i++)
    {
        x = x + h;
        f1 = x * x + 12.0f * x + 4.0f;
        s += (f0 + f1) * h / 2.0f;
        f0 = f1;
    }
    cout << "s = " << s << endl;
    return 0;
}