Create part2.fth

day09/part2.fth

@@ -0,0 +1,45 @@
+include ./util.fth
+
+: hash-pair ( x y -- h ) 
+    swap 1 lshift dup 0 < if negate 1 - then
+    swap 1 lshift dup 0 < if negate 1 - then
+    2dup >= if over dup * + + else dup * + then ;
+
+: normalize dup abs 2 = if 2 / then ;
+
+act-new value locations
+: execute-instructions ( rope-addr max fname-addr fname-len -- )
+    r/w open-file throw >r \ open file and throw fp onto rstack
+    begin pad over r@ read-line throw \ iterate through file
+    while
+        rot >r pad tuck dup c@ \ get the instruction
+        80 > -2 * 1 - \ get the sign of the direction
+        -rot 2 + swap 2 - 0 here 2swap >number throw 2drop \ get the amount of instruction
+        rot c@ dup 76 = swap 82 = or 1 + cells \ get direction
+        r@ 2swap 0 do \ loop instruction number of times
+            dup 2over + +! \ move rope by 1
+            over 9 0 do
+                2 cells + >r \ get next rope knot
+                r@ 2 cells - @ r@ @ - \ head x - tail x
+                r@ cell - @ r@ cell + @ - \ head y - tail y
+
+                2dup abs 1 > swap abs 1 > or if \ check the distance
+                    normalize swap normalize \ divide by 2 if its -2 or 2
+                    r@ +! r@ cell + +! \ increment by displacement vector
+                else 2drop then r>
+            loop drop
+            swap dup 18 cells + @ over 19 cells + @ hash-pair \ hash the tail
+            dup locations act-insert swap \ insert value into avl tree
+        loop 2drop drop r> swap 
+    repeat r> close-file throw 2drop drop ;
+
+: main 
+    20 cells dup allocate throw tuck swap erase \ create rope
+    10 s" input.txt" execute-instructions \ run instructions
+    locations act-length@ . \ print the length
+    ;
+
+: return 10 emit bye ;
+
+main
+return