实验三

#include<math.h>
#include<stdio.h>

int main() {
    float a, b, c, x1, x2;
    float delta, real, imag;

    printf("Enter a,b,c: ");

    while(scanf("%f%f%f", &a, &b, &c) != EOF) {
        if (a == 0)
            printf("not quadratic equation.\n\n");
        else {
            delta = b*b-4*a*c;

            if (delta >= 0) {
                x1 = (-b + sqrt(delta)) / (2 * a);
                x2 = (-b - sqrt(delta)) / (2 * a);
                printf("x1=%.2f,x2=%.2f\n\n", x1, x2);
            }
            else {
                real = -b / (2 * a);
                imag = sqrt(-delta) / (2 * a);
                printf("x1=%.2f+%.2fi,x2=%.2f-%.2fi\n\n", real, imag, real, imag);
            }
        }
        printf("Enter a,b,c:");
    }
    return 0;
}

 任务2

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#define N 5

int main() {
    int x, n;

    srand(time(0));
    n = 0;
    do {
        n++;
        x = rand() % 10;
        printf("%3d", x);
    } while (n < N);

    printf("\n");

    return 0;
}

 任务三

#include<math.h>
#include<stdio.h>
int main() {
    int n, c, m;
    c = 0;
    for (n = 101; n <= 200; n++)
    {
        for (m = 2; m <= sqrt(n); ++m)
            if (n % m == 0)break;
        if (m > sqrt(n))
        {
            printf("%d\t", n);
            c++;
            if (c % 5 == 0)
                printf("\n");
        }
    }
    printf("\n");
    printf("100~200之间共有%d个素数", c);
    return 0;
}

 

 任务4

#include<stdio.h>
int main()
{
    int a, b, c, d;
    d = 1;
    c = 0;
    printf("输入一个数字:");
        while (scanf("%d", &b) != EOF) {

            while (b >= 1)
            {
                a = b % 10;
                b = b / 10;
                if (a % 2 != 0)
                {
                    c = c + a * d;
                    d = d * 10;
                }
            }
                printf("新数字是%d\n", c);
                printf("输入一个数字：");
            c = 0;
            d = 1;
        }
    return 0;
}

 任务5

#include<stdio.h>
int main() {
    int a, b, c;
    float d, e;
    d = 0;
    e = 1;
    b = 1;
    c = 1;
    printf("Enter n(0~10):");
    while (scanf("%d", &a) != EOF) {

        for (b = 1; b <= a; b++)
        {
            c = (-1) * c * b;
            d = d - e / c;
        }
        printf("n=%d,d=%f\n\n", c, d);
    }
    return 0;
}

 任务六

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
int main()
{
    int a, b, c, d;
    srand(time(0));
    a = (rand() % 31 + 1);
    printf("猜猜2020年12月哪一天是你的luck day\n\n");
    printf("开始咯,你有三次机会，猜吧（1~31):");
    scanf("%d", &a);
    printf("\n\n");
    if (b == a)
    {
        printf("luck day");
    }
    else if (b < a)
    {
        printf("你猜的日期早了，luck day还没到呢");
    }
    else if (b > a)
    {
        printf("你猜的日期晚了，luck day悄悄溜到前面啦");
    }
    printf("再猜(1~31:)");
    scanf("%d", &c);
    printf("\n\n");
    if (c == a)
    {
        printf("luck day");
    }
    else if (c < a)
    {
        printf("你猜的日期早了，luck day还没到呢");
    }
    else if (c > a)
    {
        printf("你猜的日期晚了，luck day悄悄溜到前面啦");
    }
    printf("再猜(1~31:)");
    scanf("%d", d);
    printf("\n\n");
    if (d == a)
    {
        printf("luck day");
    }
    else if (d < a)
    {
        printf("你猜的日期早了，luck day还没到呢");
        printf("次数用完啦。偷偷告诉你：12月，你的luck day是%d号", a);
    }
    else if (d > a)
    {
        printf("你猜的日期晚了，luck day悄悄溜到前面啦");
        printf("次数用完啦。偷偷告诉你：12月，你的luck day是%d号", a);
    }
    return 0;
}