第五章编程练习

5-1

#include <stdio.h>
#define M_PER_H 60

int main()
{
    int total_m, hour, minutes;

    do{
        printf("Enter total minutes：");
        scanf("%d", &total_m);
        hour = total_m / M_PER_H;
        minutes = total_m % M_PER_H;
        if (total_m <= 0){
            hour = 0;
            minutes = 0;
        }
        printf("The time is:%02d:%02d.\n", hour, minutes);
    }while (total_m > 0);

    return 0;
}

/* 
Enter total minutes：123
The time is:02:03.
Enter total minutes：288
The time is:04:48.
Enter total minutes：666
The time is:11:06.
Enter total minutes：-1
The time is:00:00.

*/

 

 5-2

#include <stdio.h>

int main()
{
    int num;
    int cnt = 0;
    printf("Enter a number:");
    scanf("%d", &num);
    while (cnt <= 10){
        printf("%d\n", num+cnt );
        cnt++;
    }

    return 0;
}

5-3

#include <stdio.h>

int main()
{
    int days, day, week;
    int stop = 0;
    const int days_w = 7;
    do{
        printf("Enter days:");
        scanf("%d", &days);
        if (days <= 0){
            stop = 1;
            printf("Bye!\n");
        }else{
            printf("%d days are %d weeks, %d days.\n", days, days/days_w, days%days_w);
        }
    }while (stop == 0);
    return 0;
}

/*
Enter days:15
15 days are 2 weeks, 1 days.
Enter days:0
Bye!

*/

5-4 与5-3基本一样，略过

5-5

#include <stdio.h>

int main()
{
    int money,days;
    int TotalMoney = 0;
    int cnt = 1;

    printf("Enter days to count:");
    scanf("%d", &days);
    while(cnt++ <= days){
        printf("How much money did you make today:");
        scanf("%d", &money);
        TotalMoney = TotalMoney + money;
    }
    printf("You have made $ %d in %d days!\n", TotalMoney, days);
    return 0;
}

/*
Enter days to count:5
How much money did you make today:1
How much money did you make today:2
How much money did you make today:3
How much money did you make today:4
How much money did you make today:5
You have made $ 15 in 5 days!

*/

 5-6

#include <stdio.h>

int main()
{
    int sum, n = 0; //这种写法不对sum初始值不一定为0
    int sum =0;
    int n;
    int i = 1;

    printf("Enter a num:");
    scanf("%d", &n);
    while(i <= n){
        sum = sum + i*i;
        i++;
    }
    printf("The summary is: %d", sum);
    return 0;
}

/*
Enter a num:5
The summary is: 55
*/

5-7

#include <stdio.h>

float cube_f(float num);  //函数原型声明结尾要有;号

int main()
{
    float cube, n;

    printf("Enter a num:");
    scanf("%f", &n);
    printf("The cube of %.3f is: %.3f", n, cube_f(n));
    return 0;
}

float cube_f(float num){
    return num * num * num;
}

/*
Enter a num:3
The cube of 3.000 is: 27.000
*/

5-8 5-9 略