I found this thread rather interesting on this topic:
daniweb.com/techtalkforums/thread40450.html28
I found this to be the most interesting answers:
">and scanf() and printf() from their prototype know what kind of variables to expect.
And in what way do you think that the runtime type selection from a format string with scanf/printf is faster than selecting an overloaded function at compile time?"
any comments about this thread?
Nothing new, really.
We all know C++ streams have greater potential than scanf/printf (more knowledge about parameters at compilation time). Some day, compilers will learn to use it.
The compiler we use, under our conditions, has a much faster scanf/printf than cin/cout. That's all.
This thread, while very interesting to me, is pretty old now.
What's the news on this for late 2008?
-Oscarian
If you are using cin and cout only and no printf and scanf, then you can use
ios_base::sync_with_stdio(false);to fasten up cin and cout.
My logic tells me that iostream should be faster than printf, since how the arguments are parsed(run-time vs compile-time).
and to back it up: quora.com/C++-programming-la ... ME&share=117
I almost always use printf/scanf, because they are a lot faster. When my code gets TLE and the time complexity of the solution is similar to the complexity of the input, I use getchar_unlocked() and parse the input by myself. Even scanf -- faster than cin -- is still too slow. In SPOJ BR I got 0.5s in a problem with scanf, 0.17s with getchar and 0.02s with getchar_unlocked().
It means that, if the input is O(n²) and the expected solution is O(n²), maybe you can solve it in O(n² lg n) time just by parsing the input yourself (so, you don't spend much time with the input and get a lot of extra time for the solution). PS: I don't use atoi. Converting to integer WHILE reading the input is faster... for each algarism c you read, you update your integer to: x = 10*x + (c-'0').
A może napisać jakieś obliczenia dla pierwszego przykładu tj. 21 6 5? Bo ciągle nie rozumiem w jaki sposób obliczyć długość ciąży?
Dobry wieczór. Brałem pod uwagę wszystko co było napisane na forum. Ktoś pomoże?
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int main() {
int ile,x,y,z,i;
float miesiac;
scanf("%d",&ile);
for(i=0;i<ile;i++){
scanf("%d",&x);
scanf("%d",&y);
scanf("%d",&z);
miesiac=x+y;
miesiac=miesiac-z*y;
miesiac=miesiac/(z-1);
miesiac=miesiac*12;
miesiac=abs(miesiac);
miesiac=round(miesiac);
printf("%.0f",miesiac);
}
return 0;
}
1) jeżeli dane są całkowite i wynik ma by całkowity, to obliczenia wykonujemy na liczbach całkowitych (powtarzam to już po raz tysięczny chyba 
)
2) wzór jest zły (niedużo[color=#FF4000], trzeba trochę poprawic, gdy liczymy na liczbach całkowitych[/color])
3) czy oglądałeś wyście programu dla danych testowych - z przekierowanym wejściem z pliku, lub np. na http://ideone.com8 ?
Please stop using archaic code for the wrong reasons.
// never use endl instead of '\n' since endl forces a useless but expensive flush
#define endl '\n'
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr); // NULL if you're old fashioned.
}Voila! cin/cout is faster than scanf/printf. But if you really need speed I/O, cin.read() and parse it yourself.
Hi; I am trying to use std::cin.readsome() for very fast input. Unfortunately the solution is working on my terminal but not on some judging servers. The same solutions transated to fread() from cstdio worked perfectly…
namespace FI {
const int L = 1 << 15 | 1;
char buf[L], *front, *back;
void nextChar(char &);
template <typename T>void nextNumber(T &);
}
void FI::nextChar(char &c) {
if(front == back) std::cin.readsome(buf, L), back = (front=buf) + std::cin.gcount();
c = !std::cin.gcount() ? (char)EOF : *front++;
}
template<typename T>void FI::nextNumber(T &x) {
char c; int f = 1;
for(nextChar(c); c>'9'||c<'0'; nextChar(c)) if(c == '-') f = -1;
for(x=0; c>='0'&& c<='9'; nextChar(c)) x = x*10+c-'0';
x *= f;
}
