C++怎么实现比较日期大小

今天小编给大家分享一下C++怎么实现比较日期大小的相关知识点，内容详细，逻辑清晰，相信大部分人都还太了解这方面的知识，所以分享这篇文章给大家参考一下，希望大家阅读完这篇文章后有所收获，下面我们一起来了解一下吧。

一、目的

用来比较两个日期。日期格式：2023-03-31 09:16:56。

二、代码

//std::wstring strA = L"2023-03-31 09:16:56";
//std::wstring strB = L"2023-03-31 09:21:34";
bool LessThanEx(std::wstring strA, std::wstring strB)
{
	std::wstring strLeftA, strRightA;
	std::wstring strLeftB, strRightB;
	{
		std::wstring strLeft, strRight;
		std::size_t nIndex = strA.find(L" ");
		if (nIndex!=std::string::npos)
		{
			strLeft = strA.substr(0,nIndex);
			strRight = strA.substr(nIndex+1);

			std::wstring wsDivide = L"-";
			strLeft.replace(strLeft.find(wsDivide),wsDivide.length(),L"");
			strLeft.replace(strLeft.find(wsDivide),wsDivide.length(),L"");

			wsDivide = L":";
			strRight.replace(strRight.find(wsDivide),wsDivide.length(),L"");
			strRight.replace(strRight.find(wsDivide),wsDivide.length(),L"");
		}

		strLeftA = strLeft;
		strRightA = strRight;
	}

	{
		std::wstring strLeft, strRight;
		std::size_t nIndex = strB.find(L" ");
		if (nIndex!=std::string::npos)
		{
			strLeft = strB.substr(0,nIndex);
			strRight = strB.substr(nIndex+1);

			std::wstring wsDivide = L"-";
			strLeft.replace(strLeft.find(wsDivide),wsDivide.length(),L"");
			strLeft.replace(strLeft.find(wsDivide),wsDivide.length(),L"");

			wsDivide = L":";
			strRight.replace(strRight.find(wsDivide),wsDivide.length(),L"");
			strRight.replace(strRight.find(wsDivide),wsDivide.length(),L"");
		}

		strLeftB = strLeft;
		strRightB = strRight;
	}

	__int64 nLeftA = std::stoi(strLeftA);
	__int64 nLeftB = std::stoi(strLeftB);

	__int64 nRightA = std::stoi(strRightA);
	__int64 nRightB = std::stoi(strRightB);
	if(nLeftA < nLeftB)
	{
		return true;
	}
	else if(nLeftA > nLeftB)
	{
		return false;
	}
	else
	{
		if(nRightA >= nRightB)
		{
			return false;
		}
		
		return true;
	}

	return true;
}

//CString strA = _T("2023-03-31 09:16:56");
//CString strB = _T("2023-03-31 09:21:34");
bool LessThan(CString strA, CString strB)
{
	CString strLeftA, strRightA;
	CString strLeftB, strRightB;
	{
		CString strLeft, strRight;
		int nIndex = strA.Find(_T(" "));
		if (nIndex > -1)
		{
			strLeft = strA.Left(nIndex);
			strRight = strA.Mid(nIndex+1,strA.GetLength() - nIndex-1);

			strLeft.Replace(_T("-"),_T(""));
			strRight.Replace(_T(":"),_T(""));
		}

		strLeftA = strLeft;
		strRightA = strRight;
	}

	{
		CString strLeft, strRight;
		int nIndex = strB.Find(_T(" "));
		if (nIndex > -1)
		{
			strLeft = strB.Left(nIndex);
			strRight = strB.Mid(nIndex+1,strB.GetLength() - nIndex-1);

			strLeft.Replace(_T("-"),_T(""));
			strRight.Replace(_T(":"),_T(""));
		}

		strLeftB = strLeft;
		strRightB = strRight;
	}

	__int64 nLeftA = _tstoi64(strLeftA);
	__int64 nLeftB = _tstoi64(strLeftB);

	__int64 nRightA = _tstoi64(strRightA);
	__int64 nRightB = _tstoi64(strRightB);
	if(nLeftA < nLeftB)
	{
		return true;
	}
	else if(nLeftA > nLeftB)
	{
		return false;
	}
	else
	{
		if(nRightA >= nRightB)
		{
			return false;
		}

		return true;
	}

	return true;
}

三、补充

除了比较大小，C++还可以实现计算日期相差多少天，下面是实现代码，希望对大家有所帮助

#include <iostream>
#include <stdio.h>
#include <algorithm>
using namespace std;
bool isLeap(int year) {
	return (year % 4 == 0) && (year % 100 != 0) || (year % 400 == 0);
}
int main() {
	//定义好平年和闰年每月的天数
	int monthDays[13][2] = {
		{0,0},{31,31},{28,29},{30,30},{31,31},{30,30},
		{31,31},{30,30},{31,31},{30,30},{31,31},{30,30},
		{31,31}
	};
	int time1, year1, month2, days1;
	int time2, year2, month3, days2;
	int numbers =1;
	// 输入两个日期
	cout << "输入两个日期，空格分隔";
	cin >> time1 >> time2;
	if (time1>time2){
		int temp = time1;
		time1 = time2;
		time2 = temp;

	}
	//拆解日期，分为年，月，号
	year1 = time1 / 10000; month2 = time1 / 100 % 100; days1 = time1 % 100;
	year2 = time2 / 10000; month3 = time2 / 100 % 100; days2 = time2 % 100;
	//第一个日期 累加到 第二个日期
	while (year1 < year2 || month2 < month3 || days1 < days2) {
		days1++;// 在第一个日期基础上  加一天
		//加一天后，相应的月，年可能也要做一定的变化
		if (days1 == monthDays[month2][isLeap(year1)]+1) {//当前号超过当前月最高天数：月份加1，号变成下月的1号
			month2++;
			days1 = 1;
		}
		if (month2 == 13) {//月份超过12个月 ：年份加1,月份变成下年的1月
			year1++;
			month2 = 1;
		}
		numbers++;
	}
	cout << numbers << endl;
	return 0;
}

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