C程序正在打印太多

Question

我正在尝试运行这个程序，它要求用户以 mm/dd/yy 格式输入两个日期。在输入两个日期后，程序应该比较两个日期以查看哪个日期较大。我运行遇到的问题是，当我在同一日期输入时，代码吐出 "The dates are the same." 但它继续打印 1/1/1 早于 1/1/1（假设1/1/1 是输入两次的日期）。当代码相同时，如何跳过下一个代码？我希望程序在输入相同日期后结束。

下面是我目前的代码。我也在使用 bool，但不确定我是否使用正确。

// Preprocessor directives
#include <stdio.h>
#include <stdbool.h>


// Call main function
int main (void)
{
    // Declare variables
    int d1, m1, y1, d2, m2, y2;
    bool first_date = true;

    // Prompt user to enter information
    printf("Enter first date (mm/dd/yy): ");
    scanf("%d /%d /%d", &m1, &d1, &y1);

    printf("Enter second date (mm/dd/yy): ");
    scanf("%d /%d /%d", &m2, &d2, &y2);

    // if/else statements for comparison
    if (y1 < y2)
        first_date = true;
    else if (y1 > y2)
        first_date = false;
    else if (m1 < m2)
        first_date = true;
    else if (m1 > m2)
        first_date = false;
    else if (d1 < d2)
        first_date = true;
    else if (d1 > d2)
        first_date = false;
    else 
        printf("The dates are the same.\n");

    if (first_date == true)
    {
        printf("%d/%d/%d is earlier ijijthan %d/%d/%d\n", m1, d1, y1, m2, d2, y2);
    }
    else if (first_date == false)
    {
        printf("%d/%d/%d is earlier than %d/%d/%d\n", m2, d2, y2, m1, d1, y1);
    }



    // End program
    return(0);
}

Answer 1

这是一个逻辑问题，你需要 3 个状态而不是两个。像这样尝试

int result; /* 1 for <, 2 for > and 0 for equality */

result = 0; /* By default, they compare equal unless ... */
if (y1 < y2)
    result = 1;
else if (y1 > y2)
    result = 2;
else if (m1 < m2)
    result = 1;
else if (m1 > m2)
    result = 2;
else if (d1 < d2)
    result = 1;
else if (d1 > d2)
    result = 2;

switch (result)
{
case 1:
    printf("%d/%d/%d is earlier ijijthan %d/%d/%d\n", m1, d1, y1, m2, d2, y2);
    break;
case 2:
    printf("%d/%d/%d is earlier than %d/%d/%d\n", m2, d2, y2, m1, d1, y1);
    break;
case 3:
    printf("The dates are the same.\n");
    break;
}

您的程序运行正常，因为当程序到达 if (first_date ... 部分时 first_date 是 true。

Answer 2

一个快速解决方法是在最后两个 if 情况下添加另一个 if 语句并使用另一个 bool。然后，当您的程序打印出日期相同时，可以更新布尔值。修改后的程序看起来像这样：

// Preprocessor directives
#include <stdio.h>
#include <stdbool.h>


// Call main function
int main (void)
{
    // Declare variables
    int d1, m1, y1, d2, m2, y2;
    bool first_date = true;
    bool same = false; //NEW BOOL

    // Prompt user to enter information
    printf("Enter first date (mm/dd/yy): ");
    scanf("%d /%d /%d", &m1, &d1, &y1);

    printf("Enter second date (mm/dd/yy): ");
    scanf("%d /%d /%d", &m2, &d2, &y2);

    // if/else statements for comparison
    if (y1 < y2)
        first_date = true;
    else if (y1 > y2)
        first_date = false;
    else if (m1 < m2)
        first_date = true;
    else if (m1 > m2)
        first_date = false;
    else if (d1 < d2)
        first_date = true;
    else if (d1 > d2)
        first_date = false;
    else {
        printf("The dates are the same.\n");
        same = true; //CHANGE VALUE IF SAME
    }

    if(same == false){
        if (first_date == true)
        {
            printf("%d/%d/%d is earlier ijijthan %d/%d/%d\n", m1, d1, y1, m2, d2, y2);
        }
        else if (first_date == false)
        {
            printf("%d/%d/%d is earlier than %d/%d/%d\n", m2, d2, y2, m1, d1, y1);
        }
    }



    // End program
    return(0);
}

我认为这对你有用。

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