---
# System prepended metadata

title: C++ Note

---

# C++ Note

## I/O

### input
```cpp=
cin >> "Hello chihuahua";
```

### output
```cpp=
cout << "byebye chihuahua";
cout << "byebye" << endl; // next line
```

## string

```cpp=
#include <string>

string s;
```
輸入包含空白的整行文字，使用 getline()
以輸入 ``"Hello chihuahua!"`` 為例
```cpp=
cin >> s;
cout << s;
// Hello

getline(cin, s);
cout << s;
// Hello chihuahua!
```

---

## Vector

### create

```cpp=
#include <vector>

// vector<type> name;
vector<int> num = {1, 2, 3};
```

### .push_back()
To add a new element to the “back”, or end of the vector, we can use the `.push_back()` function.

```cpp=
num.pushback(4);

// 1, 2, 3, 4
```

### .pop_back()
You can also remove elements from the “back” of the vector using `.pop_back()`.

```cpp=
num.pop_back();

// 1, 2, 3
```

### .size()
The `.size()` function returns the number of elements in the vector.

```cpp=
num.size();

// 3
```













