C++:刷题输入

Ⅰ、规范

注意：输入是多组输入，不是一组

（1）输入预先不输入数据的组数

while(cin>>a>>b){
    cout<<a+b<<endl;
}

（2）预先知道数据组数

cin>>n;
for(int i=0; i<n; i++){
    int a,b;
    cin>>a>>b;
    cout<<a+b<<endl;
}

Ⅱ、相关输入语法

一、cin>>

用法1：输入一个数字或字符

#include <iostream>
using namespace std;
main ()
{
int a,b;
cin>>a>>b;
cout<<a+b<<endl;
}

用法2：接收一个字符串，遇“空格”、“TAB”、“回车”就结束

#include <iostream>
using namespace std;
main ()
{
char a[20];
cin>>a;
cout<<a<<endl;
}
//输入：jkljkljkl
//输出：jkljkljkl

//输入：jkljkl jkljkl       //遇空格结束
//输出：jkljkl

二、cin.getline()

用法:接收一个字符串，可以接收空格并输出

#include <iostream>
using namespace std;
main ()
{
char m[20];
cin.getline(m,5);
cout<<m<<endl;
}
//输入：jkljkljkl
//输出：jklj

//接收5个字符到m中，其中最后一个为'\0'，所以只看到4个字符输出；

//如果把5改成20：
//输入：jkljkljkl
//输出：jkljkljkl

//输入：jklf fjlsjf fjsdklf
//输出：jklf fjlsjf fjsdklf

延伸：
1、cin.getline()实际上有三个参数，cin.getline(接收字符串的变量,接收字符个数,结束字符)
2、当第三个参数省略时，系统默认为’\0’
3、如果将例子中cin.getline()改为cin.getline(m,5,‘a’);当输入jlkjkljkl时输出jklj，输入jkaljkljkl时，输出jk

三、getline()

用法：接收一个字符串，可以接收空格并输出，需包含“#include”

#include<iostream>
#include<string>
using namespace std;
main ()
{
string str;
getline(cin,str);
cout<<str<<endl;
}
//输入：jkljkljkl
//输出：jkljkljkl

//输入：jkl jfksldfj jklsjfl
//输出：jkl jfksldfj jklsjfl

四、注意的问题

1、cin.getline()属于istream流，而getline()属于string流，是不一样的两个函数

2、当同时使用cin>>,getline()时，需要注意的是，在cin>>输入流完成之后，getline()之前，需要通过

str="\n";
getline(cin,str);

的方式将回车符作为输入流cin以清除缓存，如果不这样做的话，在控制台上就不会出现getline()的输入提示，而直接跳过，因为程序默认地将之前的变量作为输入流。

看下面程序：
正常运行版本：

/*-------------Basic Input/Output-------------*/
#include<iostream>
#include<string>
#include<sstream>
using namespace std;
 
int main(){
    int age;
    //standard input(cin)
    cout<<"Please enter an integer value as your age: ";
    cin>>age;
    cout<<"Your ager is: "<<age<<".\n";
    //cin and string
    string mystr;
    cout<<"What's your name? "<<endl;
    mystr="\n";
    getline(cin,mystr);
 
    getline(cin,mystr);
    cout<<"Hello,"<<mystr<<".\n";
    char sex;
    cout<<"Please enter a F or M as your sex: ";
    cin>>sex;
    cout<<"Your sex is: "<<sex<<endl;
    cout<<"What's your favorite team? ";
    mystr="\n";
    getline(cin,mystr);
 
    getline(cin,mystr);
    cout<<"I like "<<mystr<<".\n";
 
    system("pause");
    return 0;
}
/*输出：
Please enter an integer value as your age: 16
Your ager is: 16.
What's your name?
jiaos
Hello,jiaos.
Please enter a F or M as your sex: F
Your sex is: F
What's your favorite team? programming
I like programming.
*/

非正常运行版本：

/*-------------Basic Input/Output-------------*/
#include<iostream>
#include<string>
#include<sstream>
using namespace std;

int main() {
	int age;
	//standard input(cin)
	cout << "Please enter an integer value as your age: ";
	cin >> age;
	cout << "Your ager is: " << age << ".\n";
	//cin and string
	string mystr;
	cout << "What's your name? " << endl;
	/*mystr = "\n";
	getline(cin, mystr);*/

	getline(cin, mystr);
	cout << "Hello," << mystr << ".\n";
	char sex;
	cout << "Please enter a F or M as your sex: ";
	cin >> sex;
	cout << "Your sex is: " << sex << endl;
	cout << "What's your favorite team? ";
	/*mystr = "\n";
	getline(cin, mystr);*/

	getline(cin, mystr);
	cout << "I like " << mystr << ".\n";

	system("pause");
	return 0;
}
/*输出：
Please enter an integer value as your age: 16
Your ager is: 16.
What's your name?
Hello,.
Please enter a F or M as your sex: F
Your sex is: F
What's your favorite team? I like .
*/

参考博客：
参考1
侵删