Mmn14 - numPathes

public static int numPaths (int[][] mat, int x1, int y1, int x2, int y2) {
        return numPaths(mat, x1, y1, x2, y2, 0);
    }

    private static int numPaths(int[][] mat, int x1, int y1, int x2, int y2, int counter) {
        int tmp;

        if (x1 < 0 || x2 < 0 || y1 < 0 || y2 < 0) {
            return 0;
        } else if (x1 >= mat.length || x2 >= mat.length || y1 >= mat.length || y2 >= mat.length) {
            return 0;
        } else if (mat[x1][y1] == -1 || x1 > y1) {
            return 0;
        }

        if (x1 == x2 && y1 == y2) {
            return 1;
        } else {
            tmp = mat[x1][y1];
            
            mat[x1][y1] = -1;
            counter = numPaths(mat, x1 + 1, y1, x2, y2, counter) +  
                    numPaths(mat, x1 - 1, y1, x2, y2, counter) +
                    numPaths(mat, x1, y1 + 1, x2, y2, counter) +
                    numPaths(mat, x1, y1 - 1, x2, y2, counter);

            mat[x1][y1] = tmp;

            return counter;
        }

    }