Merging Binary Trees - Amazon Top Interview Questions

Problem Statement :

Given two binary trees node0 and node1, return a merge of the two trees where each value is equal to the sum of the values of the corresponding nodes of the input trees. If only one input tree has a node in a given position, the corresponding node in the new tree should match that input node.


n ≤ 100,000 where n is the number of nodes in node0
m ≤ 100,000 where m is the number of nodes in node1

Example 1


node0 = [0, [3, null, null], [2, [3, null, null], null]]
node1 = [7, [5, null, null], [1, null, null]]


[7, [8, null, null], [3, [3, null, null], null]]

Example 2


node0 = [1, [2, [3, null, null], null], null]
node1 = [4, null, [5, null, [6, null, null]]]


[5, [2, [3, null, null], null], [5, null, [6, null, null]]]

Solution :


                        Solution in C++ :

Tree* solve(Tree* node0, Tree* node1) {
    if (!node0)
        return node1;
    else if (!node1)
        return node0;
    else {
        node0->val += node1->val;
        auto left = solve(node0->left, node1->left);
        auto right = solve(node0->right, node1->right);
        node0->left = left;
        node0->right = right;
        return node0;

                        Solution in Python : 
class Solution:
    def solve(self, node0, node1):
        if not node0:
            return node1
        if not node1:
            return node0

        node0.left = self.solve(node0.left, node1.left)
        node0.val += node1.val
        node0.right = self.solve(node0.right, node1.right)

        return node0

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