# Data Structure

## Graph To Use

### Directed Graph

### Undirected Graph

### Max number of Edges

```javascript
// undirected
n(n - 1) / 2

// directed graph
n(n - 1)
```

## Adjacent List

### Directed Graph

![](/files/qAVVBtlhoX7erzVRJfLZ)

<pre class="language-javascript"><code class="lang-javascript"><strong>const adjs = [
</strong>    [1],
    [2, 3],
    [3],
    [0]
];
</code></pre>

### Undirected Graph

above example

```javascript
const adjs = [
    [1, 3],
    [0, 2, 3],
    [1, 3],
    [0, 1, 2]
];
```

<figure><img src="/files/8zU0txPlTtdys4xysaWI" alt=""><figcaption></figcaption></figure>

```javascript
const adjs = [
    [1, 4],
    [0, 3, 4, 2],
    [1, 3],
    [1, 2, 4],
    [0, 1, 3]
];
```

reference

* <https://www.geeksforgeeks.org/print-adjacency-list-for-a-directed-graph/>
* <https://www.geeksforgeeks.org/graph-and-its-representations/>

## Matrix


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