1361. verified binary tree

There the binary tree  n nodes, from the press  0 to the  n - 1 number in which a node  i two child nodes respectively  leftChild[i] and  rightChild[i].

Only  all  nodes can be formed and  only  form  a  valid binary tree, returns  true; otherwise  false.

If the node  i is not left child, then  leftChild[i] it is equal  -1. Right child is also consistent with the rule.

Note: The node has no value, this problem using only the node number.

 

Example 1:

Input: n-=. 4, leftChild = [. 1,-1,3, -1], rightChild = [2, -1, -1, -1]
 Output: to true

Example 2:

Input: n-=. 4, leftChild = [. 1,-1,3, -1], rightChild = [2,3, -1, -1]
 Output: to false

Example 3:

Input: n-2 =, leftChild = [1,0], rightChild = [-1, -1]
 Output: to false

Example 4:

Input: n-=. 6, leftChild = [. 1, -1,-1,4-, -1, -1], rightChild = [2, -1,-1,5, -1, -1]
 Output: to false

 

prompt:

• 1 <= n <= 10^4
• leftChild.length == rightChild.length == n
• -1 <= leftChild[i], rightChild[i] <= n - 1

#include<iostream>
#include<vector>
#include<queue>
#include<algorithm>
using namespace std;
class Solution {
public:
    bool validateBinaryTreeNodes(int n, vector<int>& leftChild, vector<int>& rightChild) {
        vector<int> inDegree(n,0);
        for(int i=0;i<n;i++){
            if(leftChild[i]!=-1) inDegree[leftChild[i]]++;
            if(rightChild[i]!=-1) inDegree[rightChild[i]]++;
        }
        int root = -1;
        for(int i=0;i<n;i++){
            if(inDegree[i]!=0)continue;
            if(root != -1)return false;
            root = i;
        }
        if(root == -1 ) return false;
        queue<int> que;
        vector<bool> vi(n,false);
        vi[root]=true;
        que.push(root);
        while(!que.empty()){
            int q = que.front();
            que.pop();
            if(leftChild[q]!=-1){
                if(vi[leftChild[q]]==true) return false;
                vi[leftChild[q]]=true;
                que.push(leftChild[q]);
            }
            if(rightChild[q]!=-1){
                if(vi[rightChild[q]]==true) return false;
                vi[rightChild[q]]=true;
                que.push(rightChild[q]);
            }
        }
        return all_of(vi.begin(),vi.end(),[](const int &a){return a==1;});
    }
};
int main(){
    //freopen("D:\\YJ.txt","r",stdin);
    int n;
    cin>>n;
    vector<int> leftChild(n,0),rightChild(n,0);
    for(int i=0;i<n;i++)cin>>leftChild[i];
    for(int i=0;i<n;i++)cin>>rightChild[i];
    Solution solution;
    bool res = solution.validateBinaryTreeNodes(n, leftChild, rightChild);
    cout<<res;
    return 0;
    
}