zju code questions: 4-6

One piece function to calculate water fee

#include <stdio.h>

int main()
{
    
    
    /**
    *  定义两个
    *  定义浮点型变量
    *  y:水费
    *  x：用水的吨数
    * 
    */
    double x, y;
    printf("Enter x(x>=0):\n");
    scanf_s("%lf",&x);
    if (x <= 15) {
    
    
        y = 4 * x / 3;
    }
    else
    {
    
    
        y = 2.5 * x - 10.5;
    }
    printf("y=f(%f)=%.2f\n", x, y);
    return 0;

}

two summation

Input n, calculate the sum of 1 to n

#include <stdio.h>

int main() {
    
    
    int i,n,num;
    printf("Enter n:");
    scanf("%d",&n);
    num=0;
    for (i=1;i<=n;i++){
    
    
        num=num+i;
    }
    printf("The sum of number from 1 to %d is  %d",n,num);
}

three guessing game

#include <stdio.h>

int main() {
    
    
    int i,n,num;
    printf("Enter n:");
    scanf("%d",&n);
    int password=38;
    if(n==password){
    
    
        printf("success");
    }else{
    
    
        printf("error");
    }
    return 0;


}