C++ getchar_unlocked() VS scanf() VS cin
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getchar_unlocked( ) VS scanf() VS cin
提问by Anil Kumar Arya
What is the difference among these three input functions in programming language. Do they input in different ways from each other?
这三个输入函数在编程语言中有什么区别。他们是否以不同的方式输入？
1.getchar_unlocked()
1.getchar_unlocked()
#define getcx getchar_unlocked
inline void inp( int &n )
{
n=0;
int ch=getcx();int sign=1;
while( ch < '0' || ch > '9' ){if(ch=='-')sign=-1; ch=getcx();}
while( ch >= '0' && ch <= '9' )
n = (n<<3)+(n<<1) + ch-'0', ch=getcx();
n=n*sign;
}
2.scanf("%d",&n)
2.scanf("%d",&n)
3.cin>>n
3.cin>>n
Which one takes least time when input the integers?
输入整数时，哪一个花费的时间最少？
I use THese header files in c++ where all 3 cased run in c++;
我在 c++ 中使用这些头文件，其中所有 3 个 cased 都在 c++ 中运行；
#include<iostream>
#include<vector>
#include<set>
#include<map>
#include<queue>
#include<stack>
#include<string>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<cstdio>
#include<cmath>
#include<cstring>
#include<cstdlib>
#include<cassert>
回答by Sobhagya Mohanty
Two points to consider.
需要考虑的两点。
getchar_unlockedis deprecated in Windows because it is thread unsafe version ofgetchar().Unless speed factor is too much necessary, try to avoid
getchar_unlocked.
getchar_unlocked在 Windows 中不推荐使用，因为它是getchar().除非太需要速度因素，否则尽量避免
getchar_unlocked.
Now, as far as speed is concerned.
现在，就速度而言。
getchar_unlocked > getchar
because there is no input stream lock check in getchar_unlockedwhich makes it unsafe.
因为没有输入流锁定检查，getchar_unlocked这使得它不安全。
getchar > scanf
because getcharreads a single character of input which is char type whereas scanf can read most of the primitive types available in c.
因为getchar读取输入的单个字符是 char 类型，而 scanf 可以读取 c 中可用的大多数原始类型。
scanf > cin (>> operator)
because check this link
因为检查这个链接
So, finally
所以，最后
getchar_unlocked > getchar > scanf > cin
回答by sai krishna
I had a problem in codechef that had to input many integers abd found out that the char_unlocked() is faster than scanf which is faster than cin
我在 codechef 中遇到了一个问题，必须输入许多整数 abd 发现 char_unlocked() 比 scanf 快，而 scanf 比 cin 快
