关于快读

a_bottle @ 2019-12-22 17:53:57

int read()
{
    int x=0,q=0;
    char ch=getchar();
    if(ch=='-')
    {
        q=1;
    }
    while(ch<'0'||ch>'9')ch=getchar();
    while(ch>='0'&&ch<='9')
    {
        x=(x<<3)+(x<<1)+ch-'0';
        ch=getchar();
    }
    if(q)return -x;
    return x;
}

by A_Plus_Gu @ 2019-12-22 18:16:23

@kevinhou 不对吧

by Resonaa @ 2019-12-22 18:27:48

@OIer_Zheng

我用事实说话。

代码：

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
using namespace std;
int a,g[200000001],n;
int read()
{
    int x=0,q=0;
    char ch=getchar();
    while(ch<'0'||ch>'9')
    {
        ch=getchar();
        if(ch=='-')
        {
            q=1;
        }
    }
    while(ch>='0'&&ch<='9')
    {
        x=(x<<3)+(x<<1)+ch-'0';
        ch=getchar();
    }
    if(q) return -x;
    return x;
}
int main()
{
    srand(time(NULL));
    a=rand()*rand()%200000000+1;
    freopen("slow.in","w",stdout);
    printf("%d\n",a);
    for(int i=0;i<a;i++)
        g[i]=(rand()%2==0?-1:1)*(rand()*rand()%100000000),printf("%d ",g[i]);
    fclose(stdout);
    freopen("fast.in","w",stdout);
    printf("%d\n",a);
    for(int i=0;i<a;i++)
        printf("%d ",g[i]);
    fclose(stdout);
    freopen("con","w",stdout);
    freopen("fast.in","r",stdin);
    int t=clock();
    n=read();
    //printf("%d",n);
    for(int i=0;i<n;i++) g[i]=read();
    printf("快读用时%d\n",(clock()-t));
    fclose(stdin);
    freopen("slow.in","r",stdin);
    t=clock();
    scanf("%d",&n);
    //printf("%d",n);
    for(int i=0;i<n;i++) scanf("%d",&g[i]);
    printf("scanf用时%d\n",(clock()-t));
    return 0;
}

by 1saunoya @ 2019-12-22 18:39:42

@kevinhou fnmdp

const static int _ = 1 << 20 ;
char fin[_] , * p1 = fin , * p2 = fin ;
inline char gc() { return (p1 == p2) && (p2 = (p1 = fin) + fread(fin , 1 , _ , stdin) , p1 == p2) ? EOF : * p1 ++ ; }
inline int read() {
    bool sign = 1 ; char c = 0 ; while(c < 48) ((c = gc()) == 45) && (sign = 0) ;
    int x = (c & 15) ; while((c = gc()) > 47) x = (x << 1) + (x << 3) + (c & 15) ;
    return sign ? x : -x ;
}

by Provicy @ 2019-12-22 18:42:32

@kevinhou 你自己去做做卡常题保证以你的常数写个快读都过不去更别说scanf了/cy

by hly1204 @ 2019-12-22 18:50:43

这个快读不够快。。先要把函数名改成fast_read之类的才行吧