Jsevillamol - 8 months ago 29

Python Question

Consider a rectangular grid.

I want a short and elegant way of generating a straight path from

`[x0,y0]`

`[x1,y1]`

`x0=x1`

`y0 = y1`

For example, on input

`[1,3], [3,3]`

`[[1,3],[2,3],[3,3]`

`[3,3], [1,3]`

I have tried

`[[i,j] for i in range(self.origin[0],self.end[0]+1) for j in range(self.origin[1], self.end[1]+1)]`

Answer

Your question states that the solution from `x -> y`

should be the same as the solution `y -> x`

, i.e. we're only interested in defining the points on the path, not in any ordering of those points. If that's true, then simply find out which path has the smaller `x`

(or `y`

) and designate that as the origin.

```
origin = (3,3)
dest = (1,3)
origin, dest = sorted([origin, dest])
path = {(i,j) for i in range(origin[0], dest[0]+1) for j in range(origin[1], dest[1]+1)}
# note that this is now a set comprehension, since it doesn't make any sense
# to use a list of unique hashable items whose order is irrelevant
```

of course, this solves any obstructionless 2-D pathfinding. If you know that only one direction is changing, then only look in that direction.

```
origin, dest = sorted((origin, dest))
if origin[0] == dest[0]: # y is changing
path = {(origin[0], j) for j in range(origin[1], dest[1]+1)}
else: # x is changing
path = {(i, origin[1]) for i in range(origin[0], dest[0]+1)}
```