我只知道使用 cin 和 cout 会比 scanf 和 printf 慢。然而,最佳答案说使用 std::ios::sync_with_stdio(false) 可以比 scanf&printf 更快。然而我做了这个实验,发现不对。是我的错吗?为什么?
什么是使用 cin&cout 比 scanf&printf 更快(包括读取文件)的正确代码。谢谢。
这是我的代码:
生成数据
#include<cstdio>
#include<iostream>
#include<ctime>
#include<fstream>
#include<iomanip>
FILE *data = freopen("test.in","w",stdin);
//FILE *fi = freopen("test.in","r",stdin);
//FILE *fo = freopen("test.out","w",stdout);
int main()
{
for(int i=1;i<10000000;i++)
printf("%d\n",i);
return 0;
}
使用 scanf printf
#include<cstdio>
#include<iostream>
#include<ctime>
#include<fstream>
#include<iomanip>
//FILE *data = freopen("test.in","w",stdin);
FILE *fi = freopen("test.in","r",stdin);
FILE *fo = freopen("test.out","w",stdout);
int main()
{
int ans = 1;
while(~scanf("%d",&ans))
{
printf("%d\n",ans);
}
return 0;
}
使用 cin 和 cout ( std::ios::sync_with_stdio(true) )
#include<cstdio>
#include<iostream>
#include<ctime>
#include<fstream>
#include<iomanip>
//FILE *data = freopen("test.in","w",stdin);
FILE *fi = freopen("test.in","r",stdin);
FILE *fo = freopen("test.out","w",stdout);
int main()
{
std::ios::sync_with_stdio(true);
int ans = 1;
while(std::cin>>ans)
{
std::cout<<ans<<std::endl;
}
return 0;
}
使用 std::ios::sync_with_stdio(false)
#include<cstdio>
#include<iostream>
#include<ctime>
#include<fstream>
#include<iomanip>
//FILE *data = freopen("test.in","w",stdin);
FILE *fi = freopen("test.in","r",stdin);
FILE *fo = freopen("test.out","w",stdout);
int main()
{
std::ios::sync_with_stdio(false);
int ans = 1;
while(std::cin>>ans)
{
std::cout<<ans<<std::endl;
}
return 0;
}
Result:
scanf version: 4.918 seconds
iostream version: 51.266 seconds
iostream with sync_with_stdio(false): 31.815 seconds