polski
Task The Right-Turn Drivers' Club (kpk)
The Right-Turn Drivers' Club
Memory limit: 32 MB
We are given a rectangular city map comprising 
squares
(
and 
). The rows of
squares of the map are numbered successively from top to bottom by numbers from
to 
, and the columns from left to right successively
from 
to 
. Each square is either free or blocked.
Vehicular traffic is allowed only on free squares. From each free square one may
move to a free square adjacent to it (i.e. a square that shares a side with it),
however one is not allowed to turn back, i.e. to go back to a square
immediately after moving from 
to an adjacent square
.
The Right-Turn Drivers' Club ordered a computer program, which for any two
different squares 
and 
decides whether it is possible
to drive from 
to 
without turning left, and if so, the
program finds such a route with the minimal length. The length of a route is the
number of all its squares. The squares 
and 
are also
considered squares of the route from 
to 
.
Task
Write a program that:
- reads from the standard input data on a rectangular network of squares
(i.e. the number of rows
, the number of columns 
and
the state of each square), and next the coordinates of two different squares
and 
; - decides whether there exists a route without left turns from
to 
.
If not, the program writes one word NIE ("no") in the standard
output.
If so, the program finds one of the shortest routes without left turns and
writes it in the standard output.
If at least one of the squares 
, 
is not free, then the
answer is NIE.
Input
In the first line of the standard input there are two integers separated by a
single space: the number of rows 
and the number of columns
. In each of the following 
lines of the file there is a
description of the corresponding row of the map. Such a description has a form
of one word of length 
consisting of digits 
and
. The digit 
means that the corresponding square is
free, and the digit 
that it is blocked.
Next, in one line, there are two coordinates of the square 
,
separated by a single space: the row number not greater than 
and
the column number not greater than 
. In the following line there are
two coordinates of the square 
, written the same way.
The data in the standard input are written correctly and your program need not verify that.
Output
The following should be written in the standard output:
- either one word NIE, if there exist no route without left turns
from
to 
or at least one of the squares 
,
is blocked. - or a description of one of the routes with no left turns from
to 
having the minimal length; in that case one should write the
length of the route 
in the first line, and in each of the following
lines - two coordinates of the successive square of the route,
separated by a single space.
Examples
For the input data:
8 9 010011101 011010101 000000000 111010101 101000100 111010101 000000000 101011111 2 6 1 3
the correct result is:
NIE
For the input data:
8 9 010011101 011010101 000000000 111010101 101000100 111010101 000000000 101011111 2 6 3 8
the correct result is:
12 2 6 3 6 4 6 5 6 5 5 5 4 4 4 3 4 3 5 3 6 3 7 3 8
Task author: Piotr Chrzastowski-Wachtel.