day 5, part 2!

12023/05/05_part2.lua

@@ -1,46 +1,29 @@
---incomplete so far
 io.input("input")
 
 seeds = {}
 nseeds = {}
-
+ranges = {}
+nranges = {}
 mapi = 0
+
 for line in io.lines() do
     if mapi == 0 then
-        --[[
-        for num in line:gmatch("%d+") do
-            table.insert(seeds,tonumber(num))
+        for s,r in line:gmatch("(%d+) (%d+)") do
+            s = tonumber(s)
+            r = tonumber(r)
+            table.insert(ranges, {start=s, fin=s+r-1})
         end
-        --]]
-        --[
-        for start,range in line:gmatch("(%d+) (%d+)") do
-            start = tonumber(start)
-            range = tonumber(range)
-            for i=start,start+range-1 do
-                table.insert(seeds,i)
-            end
-        end
-        --]]
-        
     end
 
     if line:match("^$") then
         if mapi>0 then
---            print("result")
-            for i, seed in ipairs(seeds) do
-                if not nseeds[i] then
-                    nseeds[i] = seed
-                end
---                print(i, seed, "->", nseeds[i])
-            end
-            for i,seed in ipairs(nseeds) do
-                seeds[i] = seed
-            end
-            nseeds = {}
+            -- add new ranges for next iteration
+            table.move(nranges, 1, #nranges, #ranges+1, ranges)
+            nranges = {}
         end
 
         mapi = mapi + 1
-        print(mapi)
+        --print(mapi)
         goto continue 
     end
 
@@ -49,28 +32,57 @@ for line in io.lines() do
     end
 
     dst, src, len = line:match("(%d+) (%d+) (%d+)")
-    dst = tonumber(dst)
-    src = tonumber(src)
+    dsts = tonumber(dst)
+    srcs = tonumber(src)
     len = tonumber(len)
---    print(dst, src, len)
+    dstf = dsts+len-1
+    srcf = srcs+len-1
+    --print(dst, src, len, dsts, dstf, srcs, srcf)
 
-    for i, seed in ipairs(seeds) do
-        if seed >= src and seed<src+len then -- transform
-            diff = seed - src
-            nseeds[i] = dst + diff
---            print(seed,"->", dst+diff)
+    --transform
+    nextranges = {}
+    repeat
+        range = table.remove(ranges)
+        if range then
+            ns = math.max( range.start, srcs )
+            nf = math.min( range.fin, srcf )
+            if ns <= nf then -- intersection
+                --print("intersect")
+                diff = nf - ns
+                offsetsrcs = ns - srcs
+                offsetdsts = dsts + offsetsrcs
+                -- transform range
+                transformed = {start=offsetdsts, fin=offsetdsts+diff}
+                --print(ns, nf, "->", transformed.start, transformed.fin)
+                table.insert(nranges, transformed)
+                -- remainders?
+                if range.start<ns then
+                    keep = {start=range.start, fin=ns-1}
+                    --print("keep", keep.start, keep.fin)
+                    table.insert(nextranges, keep)
+                end
+                if range.fin>nf then
+                    keep = {start=nf+1, fin=range.fin}
+                    --print("keep", keep.start, keep.fin)
+                    table.insert(nextranges, keep)
+                end
+            else --range stays as is
+                table.insert(nextranges, range)
+            end
         end
-    end
+    until not range
+    -- copy next ranges to ranges
+    table.move(nextranges, 1, #nextranges, 1, ranges)
 
     ::continue::
 end
 
-print("final")
-for i,s in ipairs(seeds) do
-    if i==1 then min = s 
-    else if s<min then min=s end
-    end
-    print(i,s)
-end
-print("part 1", min)
 
+table.sort(ranges, function(a,b) return a.start < b.start end)
+--[[
+for i,r in ipairs(ranges) do
+    print(i, r.start, r.fin)
+end
+--]]
+
+print("part 2", ranges[1].start)