C++学习笔记（二） if语句_if(bool)-优快云博客

本文链接：https://blog.youkuaiyun.com/Doobe/article/details/66975103

本文详细介绍了C++中if语句的三种形式及其使用场景，包括缺省形式、完整形式和并列形式，并通过实例展示了如何应用这些形式来解决实际问题。

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C++学习笔记（二） if语句

if条件语句有三种形式：

1.一般（缺省）形式 if(bool) 语句

#include<iostream>
using namespace std;

void main()
{
	int price = 12;//定义快餐的价格为12
	int money = 0;
	cout << "快餐价格为12元，请付钱:" << endl;
	cin >> money;

	if (money >= price)
		cout << "有足够的钱购买快餐" << endl;
        system("pause");
}

2.完整形式 if(bool) {语句1} else {语句2}

#include<iostream>
using namespace std;

void main()
{
	int price = 12;//定义快餐的价格为12
	int money = 0;
	cout << "快餐价格为12元，请付钱:" << endl;
	cin >> money;

	if (money >= price)
	{
		int residue = money - price;//剩余的钱
		cout << "获得一份快餐，剩余：" << residue << "元" << endl;
	}
	else
	{
		cout << "钱不够- -" << endl;
	}
       system("pause")
}

3.并列形式 if(bool){语句1} else if(bool){语句2} ....else{语句n}

#include<iostream>
using namespace std;

void main()
{
	int price_a = 12;//定义快餐A的价格为12
	int price_b = 22;//定义快餐A的价格为22
	int money = 0;
	cout << "快餐A价格为12元，快餐B价格为22元，请付钱:" << endl;
	cin >> money;

	if (money >= price_a + price_b)
	{
		int residue = money - price_a - price_b;
		cout << "获得一份A快餐和一份B快餐，剩余：" << residue << "元" << endl;
	}
	else if (money >= price_b)
	{
		int residue = money - price_b;
		cout << "获得一份B快餐，剩余：" << residue << "元" << endl;
	}
	else if (money >= price_a)
	{
		int residue = money - price_a;
		cout << "获得一份A快餐，剩余：" << residue << "元" << endl;
	}
	else
	{
		cout << "钱不够- -" << endl;
	}
       system("pause");
}

if语句嵌套if语句

#include<iostream>
using namespace std;

void main()
{
	int bicycle = 230;
	int umbrella = 35;
	int pen = 10;
	int money = 0;
	char selecte = 0;

	cout << "商城大甩卖：" << endl;
	cout << "自行车230元，雨伞35元，钢笔10元。" << endl;

	cout << "请付钱：" << endl;
	cin >> money;
	cout << "请选择您需要的商品：a为自行车，b为雨伞，c为钢笔" << endl;
	cin >> selecte;

	if (selecte = 'a')
	{
		if (money >= bicycle)
		{
			int residue = money - bicycle;
			cout << "您已成功购买自行车，剩余：" << residue << "元" << endl;
		}
		else
		{
			cout << "金钱不够，请充值" << endl;
		}
	}
	else if (selecte = 'b')
	{
		if (money >= umbrella)
		{
			int residue = money - umbrella;
			cout << "您已成功购买雨伞，剩余：" << residue << "元" << endl;
		}
		else
		{
			cout << "金钱不够，请充值" << endl;
		}
	}
	else if (selecte = 'c')
	{
		if (money >= pen)
		{
			int residue = money - pen;
			cout << "您已成功购买钢笔，剩余：" << residue << "元" << endl;
		}
		else
		{
			cout << "金钱不够，请充值" << endl;
		}
	}
	else
	{
		cout << "请输入正确编号" << endl;
	}
       system("pause");
}

注意：如果省去｛｝只能关联一行代码。