Question

我只是想知道是否有人注意到我的代码块出错了。该程序应该是一个比较2个日期的测试程序。如果调用日期更大，则我正在处理的函数应该返回1，调用日期小于1时返回1，如果调用日期等于参数中的日期则返回0。我的考试计划：

#include <cstdlib>
#include <iostream>
#include <string>

#include "date.h"

using namespace std;

//date is initialized in a month/day/year format.

int main(int argc, char* argv[])
{
    string* d;

    date d1(4,1,4);
    date d4(4,4,4);

    int greaterTest = d4.compareTo(d1);
    int lessTest = d1.compareTo(d4);


    cout << greaterTest << endl;               //i believe these two lines are printing out a
    cout << lessTest << endl;                  //location in memory
    cout<<&d <<endl;


    system("pause");
    return EXIT_SUCCESS;
}

巨大的compareTo（）函数：

    int date::compareTo (date another_date)
{

    if (this->year == another_date.year && this->month == month && this->day < another_date.day)    //if both year and month are the same, test to see if day is less
    {

        return -1;
    }

    else if (this->year == another_date.year && this->month == month && this->day > another_date.day)   //if both year and month are the same, test to see if day is greater
    {

        return 1;
    }


    else if (this->year == another_date.year && this->month > month)                            //if the years are the same, test to see if the invoking month is greater
    {

        return 1;
    }

    else if (this->year == another_date.year && this->month < month)                            //if the years are the same, test to see if the invoking month is less
    {

        return -1;
    }


    else if (this->year > another_date.year)                                                    //test to see if the invoking year is greater
    {

        return 1;
    }

    else if (this->year < another_date.year)                                                    //test to see if the invoking year is less
    {

        return -1;
    }

    else if(this-> year == another_date.year && this-> month == another_date.month                  //test if the dates are exactly the same
        && this-> day == another_date.day)
    {

        return 0;
    } 


    //else{ return 15;}                                                                             //if none are true, return 15


}

我得到的唯一问题是当我尝试更改日期时（日期的第二个参数）。

Answer 1

我不确定这是不是问题，因为我无法测试...但是，你的compareTo函数有这一行：

this->month == month

不应该是：

this->month == another_date.month

Answer 2

在第一个if语句和下面的一些语句中，你有：

 this->month == month

这是比较月份，我认为你的意思是：

 this->month == another_date.month

此外，您无需一直使用'this'指针，

month == another_date.month

应该足够了。

Answer 3

这可能会从早期退出中受益：

int date::compareTo (date another_date)
{
    if (year > another_date.year) {
       //the invoking year is greater
       return 1;
    }

    if (year < another_date.year) {
       //the invoking year is less
       return -1;
    }

    // if we reached here, the years are the same.  Don't need to compare them for the other cases

    if (month > another_date.month) {
       return 1;
    }

    if (month < another_date.month) {
       return -1;
    }

    // if we reached here, the year and month are the same

    if (day > another_date.day) {
       return 1;
    }

    if (day < another_date.day) {
       return -1;
    }

    // if we reached here, the year and month and day are the same
    return 0;
}

一路上，剪切+粘贴错误......消失了，因为测试变得多余了。

Answer 4

我没有在原始代码中找到您的错误，因为我很难阅读。我想这就是你没找到它的原因。

这种替代方案可能更容易阅读，更容易证明是正确的：

// untested
int date::compareTo (date another_date)
{

    if (year < another_date.year) return -1;
    if (year > another_date.year) return 1;
    if (month < another_date.month) return -1;
    if (month > another_date.month) return 1;
    if (day < another_date.day) return -1;
    if (day > another_date.day) return 1;
    return 0;
}

Answer 5

除非你真的开始进行逐元素比较，否则我会将每组输入放入struct tm，然后使用mktime将这些输入转换为{{1}并直接比较两个time_t。在典型的情况下，那些将是自1970年1月1日午夜以来的秒数的32位或64位整数，因此在转换之后，比较变得微不足道。

似乎无法从我的代码块中获取正确的输出

5 个答案: