day 10, part 2!
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129
12023/10/10.lua
129
12023/10/10.lua
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@ -1,6 +1,5 @@
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io.input("input")
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function coord(j,i) return {["j"]=j, ["i"]=i} end
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function same(c1, c2)
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if c1 and c2 then return c1.j==c2.j and c1.i==c2.i end
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@ -9,6 +8,8 @@ end
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function visited(c) return map[c.j][c.i].steps>=0 end
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function in_path(c) return map[c.j][c.i].nxt end
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function two_connections(j, i) -- returns two coordinates of connected tiles
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if j<1 or j>nrows or i<1 or i>ncols then
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return nil,nil
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@ -18,26 +19,36 @@ function two_connections(j, i) -- returns two coordinates of connected tiles
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local c = tile.char
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if c=="S" then --find
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local matches = {}
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local dirs = {}
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local x, y = two_connections(j-1, i) -- north
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if same(co,x) or same(co,y) then
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print("N!")
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dirs.N = true
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table.insert(matches, coord(j-1, i))
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end
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x, y = two_connections(j+1, i) -- south
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if same(co,x) or same(co,y) then
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print("S!")
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dirs.S = true
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table.insert(matches, coord(j+1, i))
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end
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x, y = two_connections(j, i-1) -- west
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if same(co,x) or same(co,y) then
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print("W!")
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dirs.W = true
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table.insert(matches, coord(j, i-1))
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end
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x, y = two_connections(j, i+1) -- east
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if same(co,x) or same(co,y) then
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print("E!")
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dirs.E = true
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table.insert(matches, coord(j, i+1))
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end
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-- replaceS
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if dirs.N and dirs.E then newS = "L"
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elseif dirs.N and dirs.S then newS = "|"
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elseif dirs.N and dirs.W then newS = "J"
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elseif dirs.E and dirs.S then newS = "F"
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elseif dirs.E and dirs.W then newS = "-"
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elseif dirs.S and dirs.W then newS = "7"
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end
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map[j][i].char = newS
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return table.unpack(matches)
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elseif c=="|" then -- north and south
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return coord(j-1,i), coord(j+1,i)
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@ -78,25 +89,129 @@ for line in io.lines() do
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j = j + 1
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end
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nrows = j-1
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print(map[start.j][start.i].char, start.j, start.i)
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--print(nrows, ncols)
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--print(map[start.j][start.i].char, start.j, start.i)
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checking = {start}
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maxsteps = 0
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firstF = start
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repeat
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check = table.remove(checking,1)
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steps = map[check.j][check.i].steps
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if steps>maxsteps then maxsteps=steps end
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-- print(steps, "checking", check.j, check.i, map[check.j][check.i].char)
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x, y = two_connections(check.j,check.i)
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map[check.j][check.i].conns = table.pack(x,y)
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if not visited(x) then
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map[x.j][x.i].steps = steps+1
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table.insert(checking,x)
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if x.j<=firstF.j and x.i<=firstF.i then firstF = x end
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end
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if not visited(y) then
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map[y.j][y.i].steps = steps+1
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table.insert(checking,y)
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if y.j<=firstF.j and y.i<=firstF.i then firstF = y end
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end
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-- print(map[x.j][x.i].char, map[y.j][y.i].char)
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until #checking==0
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print("part 1", maxsteps, steps)
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--print(firstF.j, firstF.i, map[firstF.j][firstF.i].char)
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check = firstF
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x,y = table.unpack(map[check.j][check.i].conns)
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if x.i==check.i+1 then -- next is x
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n = x
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else
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n = y
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end
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-- create path
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repeat
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map[check.j][check.i].nxt = n
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--print(n.j, n.i, map[n.j][n.i].char)
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prev = check
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check = n
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local x,y = table.unpack(map[check.j][check.i].conns)
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if x.i==prev.i and x.j==prev.j then -- next is y
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n = y
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else
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n = x
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end
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until check.j==firstF.j and check.i == firstF.i
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count = 0
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for r=1,nrows do
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for c=1,ncols do
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--print("checking",r,c)
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local check = coord(r,c)
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local dirs = {}
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if not visited(check) then
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dirs.N = false
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for j=r-1,1,-1 do
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local coor = coord(j,c)
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if visited(coor) then
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local tile = map[coor.j][coor.i]
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local n = tile.nxt
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if (tile.char=="J" and n.j<j) or ((tile.char=="-" or tile.char=="L") and n.i>c) then
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dirs.N = true
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--print("N", r, c, j, c, tile.char, n.j, n.i, map[n.j][n.i].char)
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end
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break
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end
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end
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dirs.S = false
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for j=r+1,nrows do
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local coor = coord(j,c)
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if visited(coor) then
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local tile = map[coor.j][coor.i]
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local n = tile.nxt
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if (tile.char=="F" and n.j>j) or ((tile.char=="-" or tile.char=="7") and n.i<c) then
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dirs.S = true
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--print("S", r, c, j, c, tile.char, n.j, n.i, map[n.j][n.i].char)
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end
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break
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end
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end
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dirs.W = false
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for i=c-1,1,-1 do
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local coor = coord(r,i)
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if visited(coor) then
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local tile = map[coor.j][coor.i]
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local n = tile.nxt
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if (tile.char=="7" and n.i<i) or ((tile.char=="|" or tile.char=="J") and n.j<r) then
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dirs.W = true
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--print("W", r, c, r, i, tile.char, n.j, n.i, map[n.j][n.i].char)
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end
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break
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end
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end
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dirs.E = false
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for i=c+1,ncols do
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local coor = coord(r,i)
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if visited(coor) then
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local tile = map[coor.j][coor.i]
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local n = tile.nxt
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if (tile.char=="L" and n.i>i) or ((tile.char=="|" or tile.char=="F") and n.j>r) then
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dirs.E = true
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--print("E", r, c, r, i, tile.char, n.j, n.i, map[n.j][n.i].char)
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end
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break
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end
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end
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if dirs.N and dirs.S and dirs.E and dirs.W then
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--print("inside!", r,c)
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count = count+1
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end
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end
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end
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end
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print("part 2", count)
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