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以 SCNUOJ1728-快读/快写 为例下面对 C++, Python, Java 多种读入/输出方式进行探讨

本题是 5\times10^6 的输入和 5\times10^5 的输出 (我也想造更大的输出，但是 OJ 会说我输出超限 QwQ)

目录：

C++

朴素 cin/cout

BUFF: 不关同步流，不使用 cin.tie(0)，不使用 cout.tie(0)，不替换 endl

战绩：TLE (4490ms)

#include <bits/stdc++.h>
using namespace std;
#define sc(x) scanf("%lld", &x)
typedef long long ll;
ll n;
signed main()
{
    cin >> n;
    while (n)
    {
        ll m = min(10LL, n);
        ll x, sum = 0;
        for (ll i = 1; i <= m; ++i)
        {
            cin >> x;
            sum += x;
        }
        n -= m;
        cout << sum << endl;
    }
    return 0;
}

关闭同步流 cin/cout

BUFF: 关同步流，不使用 cin.tie(0)，不使用 cout.tie(0)，不替换 endl (用 \n 替换了也几乎没区别)

战绩：TLE (3974ms)

#include <bits/stdc++.h>
using namespace std;
#define sc(x) scanf("%lld", &x)
typedef long long ll;
ll n;
signed main()
{
    ios::sync_with_stdio(false);
    cin >> n;
    while (n)
    {
        ll m = min(10LL, n);
        ll x, sum = 0;
        for (ll i = 1; i <= m; ++i)
        {
            cin >> x;
            sum += x;
        }
        n -= m;
        cout << sum << endl;
    }
    return 0;
}

开启cin.tie(0)、替换 endl

BUFF: 关同步流，使用 cin.tie(0)，不使用 cout.tie(0)，用 \n替换 endl (不用 \n 替换几乎没区别，反而更慢)

战绩：326ms

如果开 cout.tie(0) 但不开 cin.tie(0) ，无论替不替换 endl 都没区别

在开 cin.tie(0) 的情况下，不论开不开 cout.tie(0) 都没什么区别，但是一定要用 \n替换 endl ，不然都会 TLE

#include <bits/stdc++.h>
using namespace std;
#define sc(x) scanf("%lld", &x)
typedef long long ll;
ll n;
signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> n;
    while (n)
    {
        ll m = min(10LL, n);
        ll x, sum = 0;
        for (ll i = 1; i <= m; ++i)
        {
            cin >> x;
            sum += x;
        }
        n -= m;
        cout << sum << '\n';
    }
    return 0;
}

朴素 scanf/printf

战绩：454 MS

#include <bits/stdc++.h>
using namespace std;
#define sc(x) scanf("%lld", &x)
typedef long long ll;
ll n;
signed main()
{
    sc(n);
    while (n)
    {
        ll m = min(10LL, n);
        ll x, sum = 0;
        for (ll i = 1; i <= m; ++i)
        {
            sc(x);
            sum += x;
        }
        n -= m;
        printf("%lld\n", sum);
    }
    return 0;
}

普通快读快写

战绩：155MS

如果用位运算优化快读(代码见下文，可以稍微优化到146MS)

如果再使用快写优化(代码见下文，可以稍微优化到133MS)

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
ll read()
{
    ll num = 0;
    char c = getchar(), up = c;
    while (c < '0' || c > '9')
        up = c, c = getchar();
    while (c >= '0' && c <= '9')
        num = (num << 1) + (num << 3) + (c ^ '0'), c = getchar();
    return up == '-' ? -num : num;
}
#define sc(x) x = read()
ll n;
signed main()
{
    sc(n);
    while (n)
    {
        ll m = min(10LL, n);
        ll x, sum = 0;
        for (ll i = 1; i <= m; ++i)
        {
            sc(x);
            sum += x;
        }
        n -= m;
        printf("%lld\n", sum);
    }
    return 0;
}

位运算优化：

ll read()
{
    char p = 0;
    ll r = 0, o = 0;
    for (; p < '0' || p > '9'; o |= p == '-', p = getchar())
        ;
    for (; p >= '0' && p <= '9'; r = (r << 1) + (r << 3) + (p ^ 48), p = getchar())
        ;
    return o ? (~r) + 1 : r;
}

快写：

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
ll read()
{
    char p = 0;
    ll r = 0, o = 0;
    for (; p < '0' || p > '9'; o |= p == '-', p = getchar())
        ;
    for (; p >= '0' && p <= '9'; r = (r << 1) + (r << 3) + (p ^ 48), p = getchar())
        ;
    return o ? (~r) + 1 : r;
}
void write(ll x)
{
    if (x < 0)
    {
        putchar('-');
        x = -x;
    }
    if (x > 9)
    {
        write(x / 10);
    }
    putchar(x % 10 + '0');
}
#define sc(x) x = read()
ll n;
signed main()
{
    sc(n);
    while (n)
    {
        ll m = min(10LL, n);
        ll x, sum = 0;
        for (ll i = 1; i <= m; ++i)
        {
            sc(x);
            sum += x;
        }
        n -= m;
        write(sum), putchar('\n');
    }
    return 0;
}

究极快读快写

战绩：37MS

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll MAXSIZE = 1 << 20;
char buf[MAXSIZE], *p1, *p2;
#define gc() (p1 == p2 && (p2 = (p1 = buf) + fread(buf, 1, MAXSIZE, stdin), p1 == p2) ? EOF : *p1++)
inline ll rd()
{
    ll x = 0, f = 1;
    char c = gc();
    while (!isdigit(c))
    {
        if (c == '-')
            f = -1;
        c = gc();
    }
    while (isdigit(c))
        x = x * 10 + (c ^ 48), c = gc();
    return x * f;
}
char pbuf[1 << 20], *pp = pbuf;
inline void push(const char &c)
{
    if (pp - pbuf == 1 << 20)
        fwrite(pbuf, 1, 1 << 20, stdout), pp = pbuf;
    *pp++ = c;
}
inline void write(ll x)
{
    if (x < 0)
        x = -x, push('-');
    static ll sta[35];
    ll top = 0;
    do
    {
        sta[top++] = x % 10, x /= 10;
    } while (x);
    while (top)
        push(sta[--top] + '0');
}
ll n;
signed main()
{
    n = rd();
    while (n)
    {
        ll m = min(10LL, n);
        ll x, sum = 0;
        for (ll i = 1; i <= m; ++i)
        {
            x = rd();
            sum += x;
        }
        n -= m;
        write(sum), push('\n');
    }
    fwrite(pbuf, 1, pp - pbuf, stdout);
    return 0;
}

Python

朴素读写

战绩：TLE(推测14000ms) (即使是 2\times10^4 的数据量也需要 174MS)

n = int(input()) // 10
for i in range(n):
    s = 0
    for j in range(10):
        s += int(input())
    print(s)

快读

战绩：1408MS (在 2\times10^4 的数据量需要 20MS, 估算快了十倍)

import sys

input = sys.stdin.readline
n = int(input()) // 10
for i in range(n):
    s = 0
    for j in range(10):
        s += int(input())
    print(s)

使用快写没有显著的优化：(1407MS)

import sys

input = sys.stdin.readline
print = sys.stdout.write
n = int(input()) // 10
for i in range(n):
    s = 0
    for j in range(10):
        s += int(input())
    print(str(s) + '\n')

JAVA

朴素读写

战绩：4648MS

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt() / 10;
        for (int i = 0; i < n; ++i) {
            int s = 0;
            for (int j = 0; j < 10; ++j) {
                s += sc.nextInt();
            }
            System.out.println(s);
        }
        sc.close();
    }
}

快读

战绩：2419MS

import java.io.*;

public class Main {
    static StreamTokenizer scanner = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
    // static PrintWriter out = new PrintWriter(new BufferedWriter(new
    // OutputStreamWriter(System.out)));

    public static int nextInt() throws IOException {
        scanner.nextToken();
        return (int) scanner.nval;
    }

    public static void main(String[] args) throws IOException {
        int n = nextInt() / 10;
        for (int i = 0; i < n; ++i) {
            int s = 0;
            for (int j = 0; j < 10; ++j) {
                s += nextInt();
            }
            System.out.println(s);
        }
    }
}

快读快写

战绩：679MS

import java.io.*;

public class Main {
    static StreamTokenizer scanner = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
    static PrintWriter out = new PrintWriter(new BufferedWriter(new
    OutputStreamWriter(System.out)));

    public static int nextInt() throws IOException {
        scanner.nextToken();
        return (int) scanner.nval;
    }

    public static void main(String[] args) throws IOException {
        int n = nextInt() / 10;
        for (int i = 0; i < n; ++i) {
            int s = 0;
            for (int j = 0; j < 10; ++j) {
                s += nextInt();
            }
            out.println(s);
        }
        out.close();
    }
}

嗞磁（话说原来关同步+cin.tie(0)+cout.tie(0)比scanf快（