般天高千效钢命副宁一乎？
\[
\color{#069}
\raisebox{60pt}{$\kern{2pt}\cancel{\phantom{\rule{4pt}{16.99pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{76.99pt}{$\kern{2pt}\cancel{\phantom{\rule{4pt}{6.68pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{83.68pt}{$\kern{2pt}\cancel{\phantom{\rule{4pt}{4.88pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{88.55pt}{$\kern{2pt}\cancel{\phantom{\rule{4pt}{3.90pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{92.45pt}{$\kern{2pt}\cancel{\phantom{\rule{4pt}{3.24pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{95.69pt}{$\kern{2pt}\cancel{\phantom{\rule{4pt}{2.75pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{98.44pt}{$\kern{2pt}\cancel{\phantom{\rule{4pt}{2.36pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{100.8pt}{$\kern{2pt}\cancel{\phantom{\rule{4pt}{2.03pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{102.83pt}{$\kern{2pt}\cancel{\phantom{\rule{4pt}{1.75pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{104.58pt}{$\kern{2pt}\cancel{\phantom{\rule{4.00pt}{1.50pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{106.08pt}{$\kern{2pt}\cancel{\phantom{\rule{4pt}{1.27pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{107.35pt}{$\kern{2pt}\cancel{\phantom{\rule{4pt}{1.06pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{108.42pt}{$\kern{2pt}\cancel{\phantom{\rule{4.00pt}{0.87pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{109.29pt}{$\kern{2pt}\cancel{\phantom{\rule{4.00pt}{0.68pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{109.97pt}{$\kern{2pt}\cancel{\phantom{\rule{4pt}{0.5pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{110.48pt}{$\rule{4pt}{0pt}$}\raisebox{110.81pt}{$\rule{4.00pt}{0pt}$}\raisebox{110.98pt}{$\rule{4pt}{0pt}$}\raisebox{110.81pt}{$\rule{4pt}{0pt}$}\raisebox{110.48pt}{$\rule{4.00pt}{0pt}$}\raisebox{109.97pt}{$\kern{2pt}\bcancel{\phantom{\rule{4pt}{0.5pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{109.29pt}{$\kern{2pt}\bcancel{\phantom{\rule{4pt}{0.68pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{108.42pt}{$\kern{2pt}\bcancel{\phantom{\rule{4pt}{0.87pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{107.35pt}{$\kern{2pt}\bcancel{\phantom{\rule{4.00pt}{1.06pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{106.08pt}{$\kern{2pt}\bcancel{\phantom{\rule{4pt}{1.27pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{104.58pt}{$\kern{2pt}\bcancel{\phantom{\rule{4pt}{1.50pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{102.83pt}{$\kern{2pt}\bcancel{\phantom{\rule{4.00pt}{1.75pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{100.8pt}{$\kern{2pt}\bcancel{\phantom{\rule{4pt}{2.03pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{98.44pt}{$\kern{2pt}\bcancel{\phantom{\rule{4.00pt}{2.36pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{95.69pt}{$\kern{2pt}\bcancel{\phantom{\rule{4pt}{2.75pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{92.45pt}{$\kern{2pt}\bcancel{\phantom{\rule{4.00pt}{3.24pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{88.55pt}{$\kern{2pt}\bcancel{\phantom{\rule{4pt}{3.90pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{83.68pt}{$\kern{2pt}\bcancel{\phantom{\rule{4.00pt}{4.88pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{76.99pt}{$\kern{2pt}\bcancel{\phantom{\rule{4pt}{6.68pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{60pt}{$\kern{2pt}\bcancel{\phantom{\rule{4.00pt}{16.99pt}\kern{-4pt}}}\kern{2pt}$}\kern{-140pt}\raisebox{43pt}{$\kern{2pt}\bcancel{\phantom{\rule{4pt}{16.99pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{36.32pt}{$\kern{2pt}\bcancel{\phantom{\rule{4pt}{6.68pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{31.45pt}{$\kern{2pt}\bcancel{\phantom{\rule{4pt}{4.88pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{27.55pt}{$\kern{2pt}\bcancel{\phantom{\rule{4pt}{3.90pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{24.3pt}{$\kern{2pt}\bcancel{\phantom{\rule{4pt}{3.24pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{21.56pt}{$\kern{2pt}\bcancel{\phantom{\rule{4pt}{2.75pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{19.20pt}{$\kern{2pt}\bcancel{\phantom{\rule{4pt}{2.36pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{17.17pt}{$\kern{2pt}\bcancel{\phantom{\rule{4pt}{2.03pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{15.42pt}{$\kern{2pt}\bcancel{\phantom{\rule{4pt}{1.75pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{13.92pt}{$\kern{2pt}\bcancel{\phantom{\rule{4.00pt}{1.50pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{12.65pt}{$\kern{2pt}\bcancel{\phantom{\rule{4pt}{1.27pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{11.58pt}{$\kern{2pt}\bcancel{\phantom{\rule{4pt}{1.06pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{10.71pt}{$\kern{2pt}\bcancel{\phantom{\rule{4.00pt}{0.87pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{10.03pt}{$\kern{2pt}\bcancel{\phantom{\rule{4.00pt}{0.68pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{9.52pt}{$\kern{2pt}\bcancel{\phantom{\rule{4pt}{0.5pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{9.19pt}{$\rule{4pt}{0pt}$}\raisebox{9.02pt}{$\rule{4.00pt}{0pt}$}\raisebox{9.02pt}{$\rule{4pt}{0pt}$}\raisebox{9.02pt}{$\rule{4pt}{0pt}$}\raisebox{9.19pt}{$\rule{4.00pt}{0pt}$}\raisebox{9.52pt}{$\kern{2pt}\cancel{\phantom{\rule{4pt}{0.5pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{10.03pt}{$\kern{2pt}\cancel{\phantom{\rule{4pt}{0.68pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{10.71pt}{$\kern{2pt}\cancel{\phantom{\rule{4pt}{0.87pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{11.58pt}{$\kern{2pt}\cancel{\phantom{\rule{4.00pt}{1.06pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{12.65pt}{$\kern{2pt}\cancel{\phantom{\rule{4pt}{1.27pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{13.92pt}{$\kern{2pt}\cancel{\phantom{\rule{4pt}{1.50pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{15.42pt}{$\kern{2pt}\cancel{\phantom{\rule{4.00pt}{1.75pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{17.17pt}{$\kern{2pt}\cancel{\phantom{\rule{4pt}{2.03pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{19.2pt}{$\kern{2pt}\cancel{\phantom{\rule{4.00pt}{2.36pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{21.56pt}{$\kern{2pt}\cancel{\phantom{\rule{4pt}{2.75pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{24.3pt}{$\kern{2pt}\cancel{\phantom{\rule{4.00pt}{3.24pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{27.55pt}{$\kern{2pt}\cancel{\phantom{\rule{4pt}{3.90pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{31.45pt}{$\kern{2pt}\cancel{\phantom{\rule{4.00pt}{4.88pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{36.32pt}{$\kern{2pt}\cancel{\phantom{\rule{4pt}{6.68pt}\kern{-4pt}}}\kern{2pt}$}\raisebox{43pt}{$\kern{2pt}\cancel{\phantom{\rule{4.00pt}{16.99pt}\kern{-4pt}}}\kern{2pt}$}\\[-103pt]
\Large中\raisebox{4pt}{国}
\raisebox{8pt}{收钱}
\raisebox{4pt}协会\\[3pt]
\Huge￥\\[1pt]
\kern{4pt}€\kern{6pt}\raisebox{-5pt}€\raisebox{-1pt}￡
\]

好东西

AK刘
AK刘2

你能看出这是干什么的吗

@bilibili

学习时间到

语文卷子

画图软件

部署 Hydro OJ

保留小数位数（四舍五入，两位）

1. printf("%.2lf", f);
2. cout << fixed << setprecision(2) << f;（需要 iomanip 头文件）

常用基本数据类型

int
short
long
long long
(以上可加 unsigned, signed 等)
float
double
long double
char
bool
...

%d -> int, long
%lld -> long long
%f -> float
%lf -> double
%Lf -> long double

字符串流：stringstream

例题：

现在有 \(n\) 行数字，每行数字的个数不一，求出这些数字的总和。

样例输入

5
1 2 3 4 5
5 4

样例输出

24

思路

使用 stringstream 字符串流处理每一行。

其中，stringstream 在 sstream 头文件中。

Code

#include <iostream>
#include <sstream>
using namespace std;

int main(){
  int n;
  cin >> n;
  getchar(); //cin 后要加 getchar
  int sum = 0;
  while(n--){
    string s;
    getline(cin, s);
    stringstream ss(s); // 字符串流
    int k;
    while(ss >> k)
      sum += k;
  }
  cout << sum;
  
  return 0;
}

随机函数

rand

生成一个在 \([0,\rm{RAND\_MAX}]\) 中的随机非负整数。使用时需要 #include <cstdlib>，需要用 srand() 设置种子，有一种办法是用现在时间来当作种子：srand(time(nullptr))。

rand()%n 不能保证均匀性，因为 \([0,n)\) 中的每个数在 \(0\bmod n,1\bmod n,2\bmod n,\dots,\rm{RAND\_MAX}\bmod n\) 中的出现次数可能不相同。

注意，在 Windows 系统下 \(\rm{RAND\_MAX}=2^{15}-1\)。所以要生成比 \(2^{15}-1\) 更大的数字，建议用 (rand() << 15 | rand())。

mt19937

注意，本内容仅在 C++11 及以后标准中开始使用。

是一个随机数生成器类，效用同 rand，随机数的范围同 unsigned int 类型的取值范围。

使用时用其定义一个随机数生成器即可：std::mt19937 myrand(seed)，seed 可不填，不填 seed 则会使用默认随机种子。需要生成随机数时调用 myrand() 即可返回一个随机数。

另一个类似的生成器是 mt19937_64，使用方式同 mt19937，但随机数范围扩大到了 unsigned long long 类型的取值范围。

```cpp
// 此程序随机输出一个 unsigned int。
#include <ctime>
#include <iostream>
#include <random>
using namespace std;

int main() {
mt19937 rng(time(nullptr));
cout << rng() << endl;
return 0;
}
```

shuffle

注意，本内容仅在 C++11 及以后标准中开始使用。

用于随机打乱指定序列。使用时需要 #include<algorithm>。

必须使用自定义的随机数生成器：std::shuffle(first, last, myrand)。
```cpp
// 此程序输出打乱后的数组 a。
#include <ctime>
#include <iostream>
#include <algorithm>
#include <random>
using namespace std;

int main() {
mt19937 rng(time(nullptr));
int a[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
shuffle(a, a + 10, rng);
for(int i = 0; i < 10; i++)
cout << a[i] << " ";

return 0;
}
```

uniform_int_distribution

注意，本内容仅在 C++11 及以后标准中开始使用。

生成随机整数值 \(i\)，均匀分布于闭区间 \([a,b]\)。使用自定义的随机数生成器，将生成器的随机数变换为范围内的随机数。
```cpp
// 此程序随机输出 10 个在 [1,100] 范围内的 int。
#include <ctime>
#include <iostream>
#include <random>
using namespace std;

int main() {
mt19937 rng(time(nullptr));
uniform_int_distribution<int> distrib(1, 100);
for(int i = 1; i <= 10; i++)
cout << distrib(rng) << " ";

return 0;
}
```

数据结构模板（更新中）

template<typename T>
class Stack{
    int len, maxl;
    T *a;
public:
    Stack(int maxn){
        a = new T[maxn + 5];
        maxl = maxn;
        memset(a, 0, sizeof a);
        len = 0;
    }
    bool empty(){
        return len == 0;
    }
    bool full(){
        return len >= maxl;
    }
    void clear(){
        len = 0;
    }
    void push(T x){
        if(full())
            throw "The stack is full!";
        a[++len] = x;
    }
    void pop(){
        if(empty())
            throw "The stack is empty!";
        len--;
    }
    T top(){
        if(empty())
            throw "The stack is empty!";
        return a[len];
    }
    int size(){
        return len;
    }
    ~Stack(){
        delete a;
    }
};
template<typename T>
class Queue{
    int L, R, maxl, len;
    T *a;
public:
    Queue(int maxn){
        maxn++;
        a = new T[maxn + 5];
        maxl = maxn;
        memset(a, 0, sizeof a);
        L = R = len = 0;
    }
    bool empty(){
        return L == R;
    }
    bool full(){
        return (R + 1) % maxl == L;
    }
    void clear(){
        L = R;
        len = 0;
    }
    void push(T x){
        if(full())
            throw "The queue is full!";
        R = (R + 1) % maxl;
        a[R] = x;
        len++;
    }
    void pop(){
        if(empty())
            throw "The queue is empty!";
        L = (L + 1) % maxl;
        len--;
    }
    T front(){
        if(empty())
            throw "The queue is empty!";
        return a[R];
    }
    T back(){
        if(empty())
            throw "The queue is empty!";
        return a[(L + 1) % maxl];
    }
    int size(){
        return len;
    }
    ~Queue(){
        delete a;
    }
};
template<typename T>
class BinaryHeap{
    // 默认实现小根堆
    int n, maxn;
    T *a;
public:
    BinaryHeap(int k){
        a = new T[k + 5];
        maxn = k;
        n = 0;
    }
    void up(int x){
        while(x > 1 && a[x] < a[x >> 1]) {
            std::swap(a[x], a[x >> 1]);
            x >>= 1;
        }
    }
    void down(int x){
        while((x << 1) <= n){
            int tmp = x << 1;
            if((tmp | 1) <= n && a[tmp | 1] < a[tmp])
                tmp |= 1;
            if(a[x] < a[tmp])
                break;
            std::swap(a[x], a[tmp]);
            x = tmp;
        }
    }
    bool full(){
        return n >= maxn;
    }
    bool empty(){
        return n == 0;
    }
    int size(){
        return n;
    }
    void push(T x){
        if(full())
            throw "The binary-heap is full!";
        a[++n] = x;
        up(n);
    }
    void pop(){
        if(empty())
            throw "The binary-heap is empty!";
        std::swap(a[1], a[n]);
        n--;
        down(1);
    }
    T top(){
        if(empty())
            throw "The binary-heap is empty!";
        return a[1];
    }
    ~BinaryHeap(){
        delete a;
    }
};
class DSU{
    int maxn;
    int* f;
public:
    DSU(int k){
        f = new int[k + 5ll];
        maxn = k;
        for(int i = 0; i <= maxn; i++)
            f[i] = i;
    }
    void clear(){
        for(int i = 0; i <= maxn; i++)
            f[i] = i;
    }
    int find(int x){
        return f[x] == x ? x : f[x] = find(f[x]); 
    }
    bool same(int x, int y){
        return find(x) == find(y);
    }
    void merge(int x, int y){
        x = find(x), y = find(y);
        if(x != y)
            f[x] = y;
    }
};