<p>You have <code>n</code> binary tree nodes numbered from <code>0</code> to <code>n - 1</code> where node <code>i</code> has two children <code>leftChild[i]</code> and <code>rightChild[i]</code>, return <code>true</code> if and only if <strong>all</strong> the given nodes form <strong>exactly one</strong> valid binary tree.</p>

<p>If node <code>i</code> has no left child then <code>leftChild[i]</code> will equal <code>-1</code>, similarly for the right child.</p>

<p>Note that the nodes have no values and that we only use the node numbers in this problem.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2019/08/23/1503_ex1.png" style="width: 195px; height: 287px;" />
<pre>
<strong>Input:</strong> n = 4, leftChild = [1,-1,3,-1], rightChild = [2,-1,-1,-1]
<strong>Output:</strong> true
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2019/08/23/1503_ex2.png" style="width: 183px; height: 272px;" />
<pre>
<strong>Input:</strong> n = 4, leftChild = [1,-1,3,-1], rightChild = [2,3,-1,-1]
<strong>Output:</strong> false
</pre>

<p><strong class="example">Example 3:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2019/08/23/1503_ex3.png" style="width: 82px; height: 174px;" />
<pre>
<strong>Input:</strong> n = 2, leftChild = [1,0], rightChild = [-1,-1]
<strong>Output:</strong> false
</pre>

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

<ul>
	<li><code>n == leftChild.length == rightChild.length</code></li>
	<li><code>1 &lt;= n &lt;= 10<sup>4</sup></code></li>
	<li><code>-1 &lt;= leftChild[i], rightChild[i] &lt;= n - 1</code></li>
</ul>

class Solution {
public:
    bool validateBinaryTreeNodes(int n, vector<int>& leftChild, vector<int>& rightChild) {
        map<int,int> ctp;
        map<int,vector<int>> mp;
        for(int i=0 ;i<n;i++){
            int lc = leftChild[i];
            int rc = rightChild[i];
            if(lc!=-1){
                if(ctp.count(lc)){
                    return false;
                }
                ctp[lc]=i;
                mp[i].push_back(lc);
            }
            if(rc!=-1){
                if(ctp.count(rc)){
                    return false;
                }
                ctp[rc]=i;
                mp[i].push_back(rc);
            }  
            
            
        }
        int root=-1;
        for(int i=0 ;i<n;i++){
            if(ctp.find(i)==ctp.end()){
                if(root!=-1){
                    return false;
                }
                root=i;
            }
        }
        if(root==-1){
            return false;
        }
        int count=0;
        queue<int> qu;
        vector<bool> vis(n,false);
        qu.push(root);
        count++;
        vis[root]=true;
        while(!qu.empty()){
            int node = qu.front();
            qu.pop();
            for(auto n:mp[node]){
                if(!vis[n]){
                    vis[n]=true;
                    qu.push(n);
                    count++;
                }
            }
        }
        if(count==n){
            return true;
        }
        return false;

    }
};
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