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# 0666. Path Sum IV

<https://leetcode.com/problems/path-sum-iv>

## Description

If the depth of a tree is smaller than `5`, then this tree can be represented by an array of three-digit integers. For each integer in this array:

* The hundreds digit represents the depth `d` of this node where `1 <= d <= 4`.
* The tens digit represents the position `p` of this node in the level it belongs to where `1 <= p <= 8`. The position is the same as that in a full binary tree.
* The units digit represents the value `v` of this node where `0 <= v <= 9`.

Given an array of **ascending** three-digit integers `nums` representing a binary tree with a depth smaller than `5`, return *the sum of all paths from the root towards the leaves*.

It is **guaranteed** that the given array represents a valid connected binary tree.

**Example 1:**

![](https://assets.leetcode.com/uploads/2021/04/30/pathsum4-1-tree.jpg)

```
**Input:** nums = [113,215,221]
**Output:** 12
**Explanation:** The tree that the list represents is shown.
The path sum is (3 + 5) + (3 + 1) = 12.
```

**Example 2:**

![](https://assets.leetcode.com/uploads/2021/04/30/pathsum4-2-tree.jpg)

```
**Input:** nums = [113,221]
**Output:** 4
**Explanation:** The tree that the list represents is shown. 
The path sum is (3 + 1) = 4.
```

**Constraints:**

* `1 <= nums.length <= 15`
* `110 <= nums[i] <= 489`
* `nums` represents a valid binary tree with depth less than `5`.

## ac

```java
```