Working part 2

2024/day-19/solution-2.sh

@@ -2,14 +2,10 @@
 
 TOWEL_FILE=$1
 DESIGN_FILE=$2
-TOWEL_ITER=10
 
 read -r -a TOWELS <<< "$( < "$TOWEL_FILE" tr ',' ' ' | paste -s -d " " )"
 read -r -a DESIGNS <<< "$( < "$DESIGN_FILE" paste -s -d " " )"
 
-#printf "Towel %s\n" "${TOWELS[@]}"
-#printf "Design %s\n" "${DESIGNS[@]}"
-
 # Check if towel is a viable match
 match_towel () {
   TOWEL=$1
@@ -27,64 +23,54 @@ match_towel () {
 }
 
 TOTAL_VALID=0
-declare -A UNMATCHED_TOWEL_LIST
+# Loop through designs
 for DESIGN in "${DESIGNS[@]}"
 do
+  # The idea is for each design, keep a sum of combinations
+  # for each index position of the DESIGN string
+  # Since the branches "multiply", just take the sum
+  # at the starting index, and add it to the end 
+  # of the "combined" index
+  # for each possible combination.
   printf "Starting design : %s\n" "$DESIGN"
-  declare -A MATCH_LIST
-  # Get all viable starting matches
-  for TOWEL_IDX in "${!TOWELS[@]}"
-  do
-    TOWEL=${TOWELS[$TOWEL_IDX]}
-    #printf "Testing towel: %s\n" "$TOWEL"
+  declare -A POINTER_LIST
+  POINTER_LIST[0]=1
+  POINTER_END=$(( ${#DESIGN}  ))
 
-    if match_towel "$TOWEL" "" "$DESIGN"
-    then
-      #printf "Starting match found. towel : %s\n" "$TOWEL"
-      # Copy towel list and remove the starting towel
-      read -r -a TOWEL_LIST <<< "$( printf "%s " "${TOWELS[@]}" )"
-      unset "TOWEL_LIST[$TOWEL_IDX]"
-      # Add to combinations
-      MATCH_LIST["$TOWEL"]=$( printf "%s " "${TOWEL_LIST[@]}" )
-      unset "TOWEL_LIST"
-    fi
-  done
-  if [[ ${#MATCH_LIST[@]} -eq 0 ]] ; then printf "No available starting matches.\n" ; continue ; fi
-  # Now iterate over starting matches
-  LOOP_COUNT=${#TOWELS[@]}
-  while [[ $LOOP_COUNT -gt 0 ]]
+  while true
   do
-    for TOWEL_MATCH in "${!MATCH_LIST[@]}"
+    POINTER=${#DESIGN}
+    # Pick lowest pointer value
+    for P in "${!POINTER_LIST[@]}"
     do
-      read -r -a TOWEL_LIST <<< "${MATCH_LIST[$TOWEL_MATCH]}"
-      # Iterate over towels and find subsequent match
-      for TOWEL_IDX in "${!TOWEL_LIST[@]}"
-      do
-        TOWEL=${TOWELS[$TOWEL_IDX]}
-        if match_towel "$TOWEL" "$TOWEL_MATCH" "$DESIGN"
-        then
-          #printf "Match found for %s towel : %s\n" "${TOWEL_MATCH}" "$TOWEL"
-          unset "TOWEL_LIST[$TOWEL_IDX]"
-          # Add to combinations
-          MATCH_LIST["$TOWEL_MATCH$TOWEL"]=$( printf "%s " "${TOWEL_LIST[@]}" )
-          unset "MATCH_LIST[$TOWEL_MATCH]"
-        fi
-      done
+      if [[ $P -lt $POINTER ]] 
+      then
+        POINTER=$P
+      fi
     done
-    (( LOOP_COUNT-- ))
-  done
-
-  # Calculate proper matches
-  for MATCH in "${!MATCH_LIST[@]}"
-  do
-    if [[ $MATCH == "$DESIGN" ]]
+    POINTER_VALUE=${POINTER_LIST[$POINTER]}
+    # Check if end has reached
+    if [[ $POINTER -eq $POINTER_END ]]
     then
-      printf "Match found for design %s\n" "$DESIGN"
-      (( TOTAL_VALID++ ))
+      break
     fi
-  done
 
-  # Remove matches
-  unset MATCH_LIST
+    # Loop through towels and remove earliest pointer
+    for TOWEL in "${TOWELS[@]}"
+    do
+      TOWEL_LEN=${#TOWEL}
+      END=$(( POINTER + TOWEL_LEN ))
+      if [[ ${DESIGN:$POINTER:$TOWEL_LEN} == "$TOWEL" ]]
+      then
+	POINTER_LIST[$END]=$(( ${POINTER_LIST[$END]} + POINTER_VALUE ))
+      fi
+    done
+
+    # Done looping through for specific point
+    unset "POINTER_LIST[$POINTER]" 
+  done
+  printf "Total matches for %s is %s.\n" "$DESIGN" "${POINTER_LIST[$POINTER_END]}"
+  TOTAL_VALID=$(( TOTAL_VALID + POINTER_LIST[$POINTER_END] ))
+  unset "POINTER_LIST"
 done
 printf "Total valid designs: %s\n" "$TOTAL_VALID"