diff options
Diffstat (limited to '04.lua')
| -rw-r--r-- | 04.lua | 78 |
1 files changed, 78 insertions, 0 deletions
@@ -0,0 +1,78 @@ +local input = {} + +for line in io.lines() do + local row = {} + for i = 1,#line do + -- X,M,A,S --> 1,2,3,4 + row[i] = string.find('XMAS', string.sub(line, i, i)) or 0 + end + table.insert(input, row) +end + +function compute_bounds (dx, size) + return math.max(0, -3*dx)+1, math.min(size, size-3*dx) +end + +function input:_has_xmas (i, j, di, dj) + for x = 0,3 do + if self[i+x*di][j+x*dj] ~= x+1 then + return false + end + end + return true +end + +function input:part1 () + local m = #self + local n = 0 + if m ~= 0 then n = #self[1] end + local sum = 0 + + for di = -1,1 do + local istart, iend = compute_bounds(di, m) + for dj = -1,1 do + if di ~= 0 or dj ~= 0 then + local jstart, jend = compute_bounds(dj, n) + for i = istart,iend do + for j = jstart,jend do + if self:_has_xmas(i, j, di, dj) then + sum = sum + 1 + end + end + end + end + end + end + print(sum) +end + +function input:_has_x_mas (i, j) + if self[i][j] ~= 3 then return false end + local nm = 0 + for ci = i-1,i+1,2 do + for cj = j-1,j+1,2 do + if self[ci][cj] == 2 then + nm = nm + 1 + if nm > 2 then return false end + elseif self[ci][cj] ~= 4 then + return false + end + end + end + return nm == 2 and self[i-1][j-1] ~= self[i+1][j+1] +end + +function input:part2 () + local m = #self + local n = 0 + if m ~= 0 then n = #self[1] end + local sum = 0 + for i = 2,m-1 do + for j = 2,n-1 do + if self:_has_x_mas(i, j) then sum = sum + 1 end + end + end + print(sum) +end + +return input |