Find all occurrences of a given word in a matrix

// Program to find all occurrences of the word in
// a matrix
#include <bits/stdc++.h>
using namespace std;

#define ROW 3
#define COL 5

// check whether given cell (row, col) is a valid
// cell or not.
bool isvalid(int row, int col, int prevRow, int prevCol)
{
	// return true if row number and column number
	// is in range
	return (row >= 0) && (row < ROW) &&
		(col >= 0) && (col < COL) &&
		!(row== prevRow && col == prevCol);
}

// These arrays are used to get row and column
// numbers of 8 neighboursof a given cell
int rowNum[] = {-1, -1, -1, 0, 0, 1, 1, 1};
int colNum[] = {-1, 0, 1, -1, 1, -1, 0, 1};

// A utility function to do DFS for a 2D boolean
// matrix. It only considers the 8 neighbours as
// adjacent vertices
void DFS(char mat[][COL], int row, int col,
		int prevRow, int prevCol, char* word,
		string path, int index, int n)
{
	// return if current character doesn't match with
	// the next character in the word
	if (index > n || mat[row][col] != word[index])
		return;

	//append current character position to path
	path += string(1, word[index]) + "(" + to_string(row)
			+ ", " + to_string(col) + ") ";

	// current character matches with the last character
	// in the word
	if (index == n)
	{
		cout << path << endl;
		return;
	}

	// Recur for all connected neighbours
	for (int k = 0; k < 8; ++k)
		if (isvalid(row + rowNum[k], col + colNum[k],
					prevRow, prevCol))

			DFS(mat, row + rowNum[k], col + colNum[k],
				row, col, word, path, index+1, n);
}

// The main function to find all occurrences of the
// word in a matrix
void findWords(char mat[][COL], char* word, int n)
{
	// traverse through the all cells of given matrix
	for (int i = 0; i < ROW; ++i)
		for (int j = 0; j < COL; ++j)

			// occurrence of first character in matrix
			if (mat[i][j] == word[0])

				// check and print if path exists
				DFS(mat, i, j, -1, -1, word, "", 0, n);
}

// Driver program to test above function
int main()
{
	char mat[ROW][COL]= { {'B', 'N', 'E', 'Y', 'S'},
						{'H', 'E', 'D', 'E', 'S'},
						{'S', 'G', 'N', 'D', 'E'}
						};

	char word[] ="DES";

	findWords(mat, word, strlen(word) - 1);

	return 0;
}