What is the difference between slice and array in Go?

Question

Accepted Answer

**Array** — fixed size. **Slice** — dynamic, flexible.

**Array:**
- Fixed length.
- Length is part of type.
- Value type (copied on assignment).

```go
// Array of 5 ints
var arr [5]int
arr[0] = 1

// Type includes length
var arr2 [3]int  // Different type from [5]int
```

**Slice:**
- Dynamic length.
- Reference type (points to array).
- Most common.

```go
// Slice
s := []int{1, 2, 3}
s = append(s, 4)  // Can grow

// From array
arr := [5]int{1, 2, 3, 4, 5}
slice := arr[1:4]  // [2, 3, 4]
```

**Slice structure:**
- Pointer to underlying array.
- Length.
- Capacity.

**When to use:**
- **Array** — rare, specific size known.
- **Slice** — most cases.

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