Construct Binary Tree from Preorder and Postorder Traversal | Leetcode 889

/**
 * 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 {
    int pre_idx=0;
    int post_idx=0;
public:
    TreeNode* constructFromPrePost(vector<int>& preorder, vector<int>& postorder) {
        TreeNode* curr = new TreeNode(preorder[pre_idx]);
        pre_idx++;

        if(curr->val != postorder[post_idx])
            curr->left = constructFromPrePost(preorder,postorder);
        if(curr->val != postorder[post_idx])
            curr->right = constructFromPrePost(preorder,postorder);
        
        post_idx++;
        return curr;
    }
};
/*
//JAVA
class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;
    TreeNode(int x) { val = x; }
}

class Solution {
    private int preIdx = 0;
    private int postIdx = 0;

    public TreeNode constructFromPrePost(int[] preorder, int[] postorder) {
        TreeNode curr = new TreeNode(preorder[preIdx]);
        preIdx++;

        if (curr.val != postorder[postIdx]) {
            curr.left = constructFromPrePost(preorder, postorder);
        }
        if (curr.val != postorder[postIdx]) {
            curr.right = constructFromPrePost(preorder, postorder);
        }

        postIdx++;
        return curr;
    }
}

#Python
class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

class Solution:
    def __init__(self):
        self.pre_idx = 0
        self.post_idx = 0

    def constructFromPrePost(self, preorder, postorder):
        curr = TreeNode(preorder[self.pre_idx])
        self.pre_idx += 1

        if curr.val != postorder[self.post_idx]:
            curr.left = self.constructFromPrePost(preorder, postorder)
        if curr.val != postorder[self.post_idx]:
            curr.right = self.constructFromPrePost(preorder, postorder)

        self.post_idx += 1
        return curr

*/