实验3 C语言分支语句和循环语句编程应用

#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 quatratic 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;
}

 

#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;
}

#include<stdio.h>
#include<math.h>
int main() {
    int i;
    int k = 0;
    int n;
    for (i = 101; i <= 200; i++) {
        for (k = 2; k <sqrt(i); k++) {
            if (i % k == 0)break;
        }
        if (k > sqrt(i)) {
            printf("%5d", i);
            n++;
            if (n % 5 == 0)printf("\n");
        }
    }
    printf("\n101~200之间一共有%d个素数\n", n);
    return 0;
}

#include<stdio.h>
#include<math.h>
int main() {
    long a;

    printf("Enter a number: ");
    while (scanf("%ld", &a) != EOF) {
        long b=0;
        int c, i = 0;
        while (a) {
            c = a % 10;
            
            if (c % 2){
                b += c * pow(10,i);
                
                i++;
            }a = a / 10;
            
        }
        printf("new number is:%ld\n\n", b);
        printf("Enter a number: ");
    }
    return 0;
}

 

#include<stdio.h>
#include<math.h>
int main() {
    int n;
    printf("Enter n(1~10): ");
    while (scanf("%d", &n) != EOF) {
        float x = 1.0;
        double s = 0.0;
        int m = 0;
        int i;
        for (i = 1; i <= n; i++) {
            x *= i;
            s += (1 / x) * pow(-1, m);
            m++;

        }
        printf("n=%d,s=%lf\n\n", n, s);
        printf("Enter n(1~10):");

    }
    return 0;
}

#include<stdio.h>
#include<stdlib.h>
#include<time.h>

int main(){
    int x,date,i,a=0;
    srand(time(0));
    date=rand()%31;
    printf("猜猜2020年12月哪一天会是你的lucky day\n开始喽，你有三次机会，猜吧（1~31）："); 
    for(i=1;i<=3;i++){
        scanf("%d",&x);
        if(x>date)printf("\n你猜的日期晚了，lucky day悄悄溜到前面啦");
        else if(x<date) printf("\n你猜的日期早了，lucky day还没到呢");
        else {
            a=1;
            printf("\n你猜中了！");
            break;
        };
         
        if(i!=3)printf("\n再猜（1~31）： "); 
        
    }
    if(a==0)printf("\n\n次数用完啦。偷偷告诉你：12月，你的lucky day是%d号",date);
    
    return 0;
    
}