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Challenges

# Connect the corners without 4 in a row

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Connect opposite corners of a rectangle of characters without putting 4 characters in a row.

## Input

• Two numbers, W and H, representing the width and height of the rectangle
• Each number will be in the range 2 to 70

## Output

• A rectangular grid of characters, of width W and height H
• You may choose any 2 distinct characters to represent path and background
• The output must contain 2 connected path characters in diagonally opposite corners of the grid
• Connected means there is a path from one to the other moving only between adjacent path characters
• Adjacent means 1 character away horizontally or vertically (but not both - diagonal adjacency does not count as connection for this challenge)
• The output must not contain 4 adjacent path characters in a line horizontally or vertically
• There is no limit to how many of the characters may be path characters, provided there are never 4 in a row.
• There may be redundant sections connected to the path
• There may be disconnected sections of path provided the main path meets the requirements

## Examples

These examples use # for a path character and . for the background.

### Valid examples for input 4, 3

##..
.##.
..##

.###
.#..
##..

#...
##..
.###

##.#
.###
##.#


### Invalid examples for input 4, 3

4 in a line horizontally:

#...
####
...#

Depends on diagonal adjacency, which does not count as connection:

#...
.#..
..##

Does not connect diagonally opposite corners:
###.
..##
###.


### Valid examples for input 7, 5

###....
..#....
..###..
....#..
....###

##.....
.##....
..##...
...##..
....###

#......
#......
##.###.
.#.#.##
.###..#

###....
..###..
###.###
#...#.#
###...#


### Invalid examples for input 7, 5

Does not connect two diagonally opposite corners:

###....
..###..
....###
...##..
...#...

Has 4 in a row horizontally:

####...
...#...
...###.
.....#.
.....##

Has 4 in a row vertically:

###....
..#....
..#.###
..###.#
......#

Depends on diagonal adjacency, which does not count as connection:

##.....
..##...
....##.
......#
......#


## Validator

You can check a specific output using this path validator, which will give a reason for any failed validations.

Explanations are optional, but I'm more likely to upvote answers that have one.

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