Anti-Diagonal Matrix Traversal (Medium) — Practice with Code Visualizer

You are given a 2D integer array nums representing a jagged matrix (rows may have different lengths). Your task is to traverse and collect all elements following an anti-diagonal pattern, starting from the top-left corner.

An anti-diagonal consists of elements where the sum of their row and column indices is constant. The traversal proceeds as follows:

Begin with the first anti-diagonal containing only the element at position (0, 0).
For each subsequent anti-diagonal, elements are collected starting from the bottom-most row and moving upward-right (i.e., row decreases while column increases).
Continue until all elements in the matrix have been visited.

This pattern effectively traverses the matrix in wave-like anti-diagonal sweeps, where each wave moves from lower-left to upper-right within that diagonal group.

Key Insight: The defining property of anti-diagonals is that all elements on the same anti-diagonal share the same value of (row + column). Elements are ordered within each anti-diagonal by their row index in descending order (bottom to top).

The anti-diagonals are: [1], [4,2], [7,5,3], [8,6], [9]. Reading each from bottom to top gives the result. For example, the anti-diagonal with sum=2 contains elements at (2,0)=7, (1,1)=5, (0,2)=3, collected in that order.

This is a jagged matrix where rows have varying lengths. The anti-diagonals are: [1], [6,2], [8,7,3], [9,4], [12,10,5], [13,11], [14], [15], [16]. Notice that missing elements (like row 2 column 1) are simply skipped, demonstrating how the algorithm handles irregular row lengths gracefully.

For this 2x2 matrix, the anti-diagonals are: [1], [3,2], [4]. The middle anti-diagonal contains (1,0)=3 before (0,1)=2 since we process bottom to top.

An anti-diagonal consists of elements where the sum of their row and column indices is constant. The traversal proceeds as follows:

Begin with the first anti-diagonal containing only the element at position (0, 0).
For each subsequent anti-diagonal, elements are collected starting from the bottom-most row and moving upward-right (i.e., row decreases while column increases).
Continue until all elements in the matrix have been visited.

This pattern effectively traverses the matrix in wave-like anti-diagonal sweeps, where each wave moves from lower-left to upper-right within that diagonal group.

For this 2x2 matrix, the anti-diagonals are: [1], [3,2], [4]. The middle anti-diagonal contains (1,0)=3 before (0,1)=2 since we process bottom to top.

Anti-Diagonal Matrix Traversal

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Anti-Diagonal Matrix Traversal

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