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# 0470. Implement Rand10(solutions/) Using Rand7(solutions/)

<https://leetcode.com/problems/implement-rand10-using-rand7>

## Description

Given the **API** `rand7()` that generates a uniform random integer in the range `[1, 7]`, write a function `rand10()` that generates a uniform random integer in the range `[1, 10]`. You can only call the API `rand7()`, and you shouldn't call any other API. Please **do not** use a language's built-in random API.

Each test case will have one **internal** argument `n`, the number of times that your implemented function `rand10()` will be called while testing. Note that this is **not an argument** passed to `rand10()`.

**Follow up:**

* What is the [expected value](https://en.wikipedia.org/wiki/Expected_value) for the number of calls to `rand7()` function?
* Could you minimize the number of calls to `rand7()`?

**Example 1:**

```
**Input:** n = 1
**Output:** [2]
```

**Example 2:**

```
**Input:** n = 2
**Output:** [2,8]
```

**Example 3:**

```
**Input:** n = 3
**Output:** [3,8,10]
```

**Constraints:**

* `1 <= n <= 105`

## ac

```java
```