Path Sum IV
<p>If the depth of a tree is smaller than <code>5</code>, then this tree can be represented by an array of three-digit integers. You are given an <strong>ascending </strong>array <code>nums</code> consisting of three-digit integers representing a binary tree with a depth smaller than <code>5</code>, where for each integer:</p>

<ul>
	<li>The hundreds digit represents the depth <code>d</code> of this node, where <code>1 &lt;= d &lt;= 4</code>.</li>
	<li>The tens digit represents the position <code>p</code> of this node within its level, where <code>1 &lt;= p &lt;= 8</code>, corresponding to its position in a <strong>full binary tree</strong>.</li>
	<li>The units digit represents the value <code>v</code> of this node, where <code>0 &lt;= v &lt;= 9</code>.</li>
</ul>

<p>Return the <strong>sum</strong> of <strong>all paths</strong> from the <strong>root</strong> towards the <strong>leaves</strong>.</p>

<p>It is <strong>guaranteed</strong> that the given array represents a valid connected binary tree.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<p><img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0600-0699/0666.Path%20Sum%20IV/images/pathsum4-1-tree.jpg" style="width: 212px; height: 183px;" /></p>

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">nums = [113,215,221]</span></p>

<p><strong>Output:</strong> <span class="example-io">12</span></p>

<p><strong>Explanation:</strong></p>

<p>The tree that the list represents is shown.<br />
The path sum is (3 + 5) + (3 + 1) = 12.</p>
</div>

<p><strong class="example">Example 2:</strong></p>

<p><img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0600-0699/0666.Path%20Sum%20IV/images/pathsum4-2-tree.jpg" style="width: 132px; height: 183px;" /></p>

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">nums = [113,221]</span></p>

<p><strong>Output:</strong> <span class="example-io">4</span></p>

<p><strong>Explanation:</strong></p>

<p>The tree that the list represents is shown.&nbsp;<br />
The path sum is (3 + 1) = 4.</p>
</div>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= nums.length &lt;= 15</code></li>
	<li><code>110 &lt;= nums[i] &lt;= 489</code></li>
	<li><code>nums</code> represents a valid binary tree with depth less than <code>5</code>.</li>
	<li><code>nums</code> is sorted in ascending order.</li>
</ul>
Tree; Depth-First Search; Array; Hash Table; Binary Tree
class Solution {
public:
    int ans;
    unordered_map<int, int> mp;

    int pathSum(vector<int>& nums) {
        ans = 0;
        mp.clear();
        for (int num : nums) mp[num / 10] = num % 10;
        dfs(11, 0);
        return ans;
    }

    void dfs(int node, int t) {
        if (!mp.count(node)) return;
        t += mp[node];
        int d = node / 10, p = node % 10;
        int l = (d + 1) * 10 + (p * 2) - 1;
        int r = l + 1;
        if (!mp.count(l) && !mp.count(r)) {
            ans += t;
            return;
        }
        dfs(l, t);
        dfs(r, t);
    }
};