Doubt on leetcode problem

#1

problem link=

solu=lass Solution {
public:
int ans = 0;

vector<int>postorder(TreeNode* root){
    
    if(root == NULL)
        return {-1, -1};
    
    int left = postorder(root->left)[1] + 1;
    int right = postorder(root->right)[0] + 1;
    
    ans = max({ans, left, right});
    return {left, right};
}

int longestZigZag(TreeNode* root) {
    
    postorder(root);
    return ans;
}

};

In this above solution can u plz tell me why is the root->left is taken at index 1 pos and the root->right is taken at index 0 position

#2

hello @Somasree

here u have alredy taken left so ur next step should be right for zig zag path that is the reason why we are looing for right(index 1) here.

and index 0 here

#3

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