Untitled

using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

namespace NumberMatchSolver;

public static class FastMatchFinder
{
    private static readonly List<(int startRow, int startCol, int endRow, int endCol, int number)> ConnectedPairs 
        = new(100);
    
    public static List<(int startRow, int startCol, int endRow, int endCol, int number)> Solve(int[][] grid)
    {
        if (grid == null || grid.Length == 0)
            return new List<(int startRow, int startCol, int endRow, int endCol, int number)>();

        ConnectedPairs.Clear();

        int totalRows = grid.Length;
        int totalCols = grid[0].Length;

        for (int row = 0; row < totalRows; row++)
        {
            for (int col = 0; col < totalCols; col++)
            {
                int currentNumber = grid[row][col];

                if (currentNumber == 0)
                    continue;
                
                int[] rowDirections = { 0, 1, 1, -1 };
                int[] colDirections = { 1, 0, 1, 1 };

                for (int directionIndex = 0; directionIndex < 4; directionIndex++)
                {
                    int rowStep = rowDirections[directionIndex];
                    int colStep = colDirections[directionIndex];
                    int nextRow = row + rowStep;
                    int nextCol = col + colStep;

                    while (nextRow >= 0 && nextRow < totalRows && nextCol >= 0 && nextCol < totalCols)
                    {
                        int nextNumber = grid[nextRow][nextCol];

                        if (nextNumber == currentNumber)
                        {
                            ConnectedPairs.Add((row, col, nextRow, nextCol, currentNumber));
                            break;
                        }
                        
                        if (nextNumber != 0)
                        {
                            break;
                        }

                        nextRow += rowStep;
                        nextCol += colStep;
                    }
                }
            }
        }
        
        return new List<(int startRow, int startCol, int endRow, int endCol, int number)>(ConnectedPairs);
    }
}