<p>You are given the <code>root</code> of a binary tree and an integer <code>distance</code>. A pair of two different <strong>leaf</strong> nodes of a binary tree is said to be good if the length of <strong>the shortest path</strong> between them is less than or equal to <code>distance</code>.</p>

<p>Return <em>the number of good leaf node pairs</em> in the tree.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/07/09/e1.jpg" style="width: 250px; height: 250px;" />
<pre>
<strong>Input:</strong> root = [1,2,3,null,4], distance = 3
<strong>Output:</strong> 1
<strong>Explanation:</strong> The leaf nodes of the tree are 3 and 4 and the length of the shortest path between them is 3. This is the only good pair.
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/07/09/e2.jpg" style="width: 250px; height: 182px;" />
<pre>
<strong>Input:</strong> root = [1,2,3,4,5,6,7], distance = 3
<strong>Output:</strong> 2
<strong>Explanation:</strong> The good pairs are [4,5] and [6,7] with shortest path = 2. The pair [4,6] is not good because the length of ther shortest path between them is 4.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> root = [7,1,4,6,null,5,3,null,null,null,null,null,2], distance = 3
<strong>Output:</strong> 1
<strong>Explanation:</strong> The only good pair is [2,5].
</pre>

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

<ul>
	<li>The number of nodes in the <code>tree</code> is in the range <code>[1, 2<sup>10</sup>].</code></li>
	<li><code>1 &lt;= Node.val &lt;= 100</code></li>
	<li><code>1 &lt;= distance &lt;= 10</code></li>
</ul>

#define SOL_v2
// #define SOL_v1
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
#ifdef SOL_v2 
    void CreateEndPatch(TreeNode* node , unordered_set<string>& pathmap, string currentpath){
        if (!node)
            return ; 
        bool isend = 1;
        if (node->left){
            CreateEndPatch(node->left, pathmap, ( currentpath + "L") );
            isend = 0;
        }
        if (node->right){
            CreateEndPatch(node->right, pathmap, ( currentpath + "R") );
            isend = 0;
        }
        if (isend){
            //cout << "set path : " << node->val << ", "<< currentpath << endl; 
            pathmap.insert(currentpath);
        }

        return ;



    }

    int Couuntdis(string str1, string str2){
        while (str1.size() && str2.size() && str1.at(0) == str2.at(0)){
            str1.erase(str1.begin());
            str2.erase(str2.begin());
        }
        return str1.size() + str2.size();

    }

    int countPairs(TreeNode* root, int distance) {
        unordered_set<string> EndPath;
        int paircount = 0 ;
        CreateEndPatch(root, EndPath, "");

        cout << EndPath.size() << endl; 
        for (unordered_set<string>::const_iterator it=EndPath.begin() ; it != EndPath.end(); it ++ ){
            for (unordered_set<string>::const_iterator it_cmp=EndPath.begin() ; it_cmp != EndPath.end(); it_cmp ++ ){
                if ( *it == *it_cmp ){
                    continue ; 
                }
                if ( Couuntdis(*it, *it_cmp) <=  distance) {
                    paircount++;
                }
            }

        }
        return paircount/2 ;
    }

    
#endif

#ifdef SOL_v1 // Fail, Because the question didnot said distinct number
    void CreateEndPatch(TreeNode* node , unordered_map<int, string>& pathmap, string currentpath){
        if (!node)
            return ; 
        bool isend = 1;
        if (node->left){
            CreateEndPatch(node->left, pathmap, ( currentpath + "L") );
            isend = 0;
        }
        if (node->right){
            CreateEndPatch(node->right, pathmap, ( currentpath + "R") );
            isend = 0;
        }
        if (isend){
            //cout << "set path : " << node->val << ", "<< currentpath << endl; 
            pathmap[node->val] = currentpath;
        }

        return ;



    }

    int Couuntdis(string str1, string str2){
        while (str1.size() && str2.size() && str1.at(0) == str2.at(0)){
            str1.erase(str1.begin());
            str2.erase(str2.begin());
        }
        return str1.size() + str2.size();

    }

    int countPairs(TreeNode* root, int distance) {
        unordered_map<int, string> EndPath;
        int paircount = 0 ;
        CreateEndPatch(root, EndPath, "");

        cout << EndPath.size() << endl; 
        for (unordered_map<int, string>::const_iterator it=EndPath.begin() ; it != EndPath.end(); it ++ ){
            for (unordered_map<int, string>::const_iterator it_cmp=EndPath.begin() ; it_cmp != EndPath.end(); it_cmp ++ ){
                if ( it->second == it_cmp->second ){
                    continue ; 
                }
                if ( Couuntdis(it->second, it_cmp->second) <=  distance) {
                    paircount++;
                }
            }

        }
        return paircount/2 ;
    }

    
#endif
};
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