C++循环语句

简介C++的循环语句

1. for循环

基本语法

for (size_t i = 0; i < count; i++)
{
    /* code */
}

用法：

#include <iostream>
using namespace std;

int main()
{
	uint32_t sum = 0;
	for(size_t i = 0;i < 10; i++)
	{
		sum+=i;
	}
	cout<<"sum is: "<<sum<<endl;

    return 0;
}

for + auto关键字，可以进行遍历

#include <iostream>
#include <vector>
#include <string>
using namespace std;

int main()
{
	std::vector<std::string> v;
	v.emplace_back("C++");
	v.emplace_back("Java");
	v.emplace_back("Python");
	v.emplace_back("C");
	
	for(auto au : v)
	{
		cout<<au<<endl;
	}
    return 0;
}

2. while循环

满足条件才会执行
基本语法

while (/* condition */)
{
    /* code */
}

用法

#include <iostream>
using namespace std;

int main()
{
	uint32_t sum = 0;
	uint32_t count = 0;
	while(sum < 100)
	{		
		sum+=count;
		count++;
	}
	cout<<"sum is: "<<sum<<endl;
	cout<<"count is: "<<count<<endl;

    return 0;
}

3. do while循环

do while循环至少执行一次
基本语法

do
{
    /* code */
} while (/* condition */);

用法

#include <iostream>
using namespace std;

int main()
{
	uint32_t sum = 0;
	uint32_t count = 0;
	do
	{
		sum+=count;
		count++;
	} while(sum < 100);	
	
	cout<<"sum is: "<<sum<<endl;
	cout<<"count is: "<<count<<endl;

    return 0;
}

do while代替多条件判读，避免频繁的if else

#include <iostream>
using namespace std;

int main()
{
	int32_t t = 1;
	
	do
	{
		if(0 == t)
		{
			cout<<"t is 0"<<endl;
			break;
		}
		if(1 == t)
		{
			cout<<"t is 1"<<endl;
			break;
		}
		if(2 == t)
		{
			cout<<"t is 2"<<endl;
			break;
		}		
	} while(0);		

    return 0;
}

辅助定义辅助的宏

#include <iostream>
using namespace std;

void fun1()
{
	cout<<"fun1"<<endl;
}

void fun2()
{
	cout<<"fun2"<<endl;	
}

#define FUNCTION() \
do{  \
   fun1(); \
   fun2(); \
}while(0)
   

int main()
{
	int32_t t = 1;
	
	if(1 == t)
	{
		FUNCTION();
	}
    return 0;
}

4. 其他

循环语句常用关键字

continue;    //终止本次循环，进行下一次循环
break;       //跳出循环，执行循环之后的语句