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Grokking the Coding Interview Patterns in C++

Solution: Minimum Moves to Spread Stones Over Grid

Explore the backtracking technique to solve the problem of equally distributing stones on a 3x3 grid. This lesson guides you through identifying empty and extra stone cells, calculating moves with Manhattan distance, and recursively finding the minimum moves needed to achieve one stone per cell. You will learn to implement and optimize this combinatorial solution effectively.

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Statement

Given a 2D grid of integers of size (3×33 \times 3), where each value represents the number of stones in the given cell, return the minimum number of moves required to place exactly one stone in each grid cell.

Constraints:

  • Only one stone can be moved in one move.

  • Stone from a cell can only be moved to another cell if they are adjacent (share a side).

  • The sum of all stones in the grid must be equal to 99.

  • grid.length, grid[i].length ...