C 嗨，我正在写一个程序，显示一年是否是一个飞跃，以及它的数字总和是多少

我理解用来判断某件事是否是闰年的代码行，我见过用来确定数字总和的代码行，但我不知道如何将两者结合起来。当我运行它时，我得到一个错误

In function "main":
error. "else" without a previous "if"
error. "else" without a previous "if"

代码：

---

代码中有几个问题-

问题1-

如果程序中的语句包含多个语句，但尚未将它们括在{}中

问题2-

您正在修改year变量的值，如果发现年份为闰年，则将其打印。因此，年的值将始终打印为0。 备份可变年份值，然后执行步骤计算总和，并在printf中打印备份值

#include <stdio.h>

int main()
{

    int year,sum=0,r;
    int year_val;

    printf("Enter a year to check if it is a leap year\n");
    scanf("%d", &year);
    year_val = year;

    if ( year%400 == 0) {
            for(;year!=0;year=year/10){
                    r=year%10;
                    sum=sum+r;
            }
            printf("%d is a leap year and the sum is %d.\n", year_val,sum);
    } else if ( year%100 == 0)
            printf("%d is not a leap year.\n", year);
    else if ( year%4 == 0 ) {
            for(;year!=0;year=year/10){
                    r=year%10;
                    sum=sum+r;
            }
            printf("%d is a leap year and the sum is %d.\n", year_val,sum);
    } else
            printf("%d is not a leap year.\n", year);
    return 0;
}

---

在代码中，对于某些if语句，您不使用带有{}对的块语法。后来插入了一些额外的printf语句，打破了语法

鉴于您的技能水平，最好始终对所有复合语句使用块语法。依我看，即使是高级程序员也不应该对任何东西使用单语句语法，除非是最简单的复合语句（如果有的话）

该年的输出不正确，因为您修改了for循环中的变量。使用另一个变量进行此计算

以下是修改后的代码：

#include <stdio.h>

int main(void) {
    int year, sum = 0, y, r;

    printf("Enter a year to check if it is a leap year\n");
    scanf("%d", &year);
    if (year % 400 == 0) {
        for (y = year; y != 0; y = y / 10) {
            r = y % 10;
            sum = sum + r;
        }
        printf("%d is a leap year and the sum is %d.\n", year, sum);
    } else
    if (year % 100 == 0) {
        printf("%d is not a leap year.\n", year);
    } else
    if (year % 4 == 0) {
        for (y = year; y != 0; y = y / 10) {
            r = year % 10;
            sum = sum + r;
        }
        printf("%d is a leap year and the sum is %d.\n", year, sum);
    } else {
        printf("%d is not a leap year.\n", year);
    }
    return 0;
}

请注意，可以根据公历对闰年进行复合测试来简化代码：

#include <stdio.h>

int main(void) {
    int year, sum, y, r;

    printf("Enter a year to check if it is a leap year\n");
    if (scanf("%d", &year) == 1) {
        if (year % 400 == 0 || (year % 4 == 0 && year % 100 != 0)) {
            for (sum = 0, y = year; y != 0; y = y / 10) {
                r = y % 10;
                sum = sum + r;
            }
            printf("%d is a leap year and the sum is %d.\n", year, sum);
        } else {
            printf("%d is not a leap year.\n", year);
        }
    } else {
        printf("input error.\n");
    }
    return 0;
}

---

代码中有很多语法错误。首先，尝试编写干净的代码

以下是您需要更正的错误

a删除第5行多余的分号 b在第8,18行为if语句添加大括号{} c添加一个临时变量来保存年份，这样，如果年份是闰年， 你可以在那里打印temp。因为年份变量随后将减少为0。

我刚刚纠正了上面提到的事情，现在你的代码工作得很有魅力

这是修改后的代码。获取大括号{}的详细信息

#include <stdio.h>
int main()
{
    int year,sum=0,r;

    printf("Enter a year to check if it is a leap year\n");
    scanf("%d", &year);
    int temp = year;
    if ( year%400 == 0){
      for(;year!=0;year=year/10){
        r=year%10;
        sum=sum+r;
        }
    printf("%d is a leap year and the sum is %d.\n", temp,sum);
    }
    else if ( year%100 == 0)
        printf("%d is not a leap year.\n", year);
    else if ( year%4 == 0 ){
        for(;year!=0;year=year/10){
            r=year%10;
            sum=sum+r;
        }
    printf("%d is a leap year and the sum is %d.\n", temp,sum);
    }

    else
        printf("%d is not a leap year.\n", year);  
    return 0;
}

---

缩进你的代码，也许你会发现不匹配的地方。

#include <stdio.h>
int main()
{
    int year,sum=0,r;

    printf("Enter a year to check if it is a leap year\n");
    scanf("%d", &year);
    int temp = year;
    if ( year%400 == 0){
      for(;year!=0;year=year/10){
        r=year%10;
        sum=sum+r;
        }
    printf("%d is a leap year and the sum is %d.\n", temp,sum);
    }
    else if ( year%100 == 0)
        printf("%d is not a leap year.\n", year);
    else if ( year%4 == 0 ){
        for(;year!=0;year=year/10){
            r=year%10;
            sum=sum+r;
        }
    printf("%d is a leap year and the sum is %d.\n", temp,sum);
    }

    else
        printf("%d is not a leap year.\n", year);  
    return 0;
}