Problem Description

You are presented with two independent coding tasks.

Task 1: In-order Traversal of a Binary Tree

Given the root of a binary tree, return an array or list containing the node values in in-order traversal.

• In-order traversal definition: Process the left subtree, then visit the current node, then process the right subtree.
• Input: root of the binary tree (may be null).
• Output: An array or list of node values.
• Constraints:
  • The tree can have up to approximately 10^5 nodes.
  • Node values fit within a 32-bit integer.

Task 2: Sum of Top-Left Submatrix up to (x, y)

Given an m x n matrix A of integers and a coordinate (x, y) (0-indexed), compute the sum of all elements within the rectangle from (0,0) to (x,y) inclusive.

• Definition: sum(x,y) = Σ_{i=0..x} Σ_{j=0..y} A[i][j]
• Input:
  • An m x n matrix A of integers.
  • One or more queries, each specifying coordinates (x, y), where 0 ≤ x < m and 0 ≤ y < n.
• Output: For each query, return the computed sum.
• Follow-up: If there are many queries, design a solution for fast per-query time.
• Constraints:
  • Dimensions m and n can be up to 10^3 or higher.
  • Matrix elements can be negative.
  • Intermediate and final sums may require a 64-bit integer type to prevent overflow.