Not working part 2

2024/day-8/solution-2.sh

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+#!/usr/bin/env bash
+
+FILE=input
+LEN=$( head -1 "$FILE" | sed -E 's/(.)/\1\ /g' | awk '{printf NF}' )
+
+read -r -a MAP_ARRAY <<< "$( < "$FILE" sed -E 's/(.)/\1\ /g' | paste -s -d ' ' )"
+read -r -a SHADOW_ARRAY <<< "$( < "$FILE" sed -E 's/(.)/\1\ /g' | paste -s -d ' ' )"
+#printf "MAP_LEN: %s, NF: %s\n" "${#MAP_ARRAY[@]}" "$LEN" >&2
+
+for CHAR in $( < "$FILE" grep -Eo '[^\.]' | sort -u | paste -s -d' ' )
+do
+  # Get indices for antennae
+  LINE="$( 
+    for (( i=0; i<${#MAP_ARRAY[@]}; i++ ))
+    do
+    if [[ ${MAP_ARRAY[i]} == "$CHAR" ]]
+    then
+      printf "%s " "$i"
+    fi
+    done
+  )"
+  #printf "%s\n" "$LINE" >&2
+  read -r -a IDX_ARRAY <<< "$LINE"
+  #printf "idx:  %s " "${IDX_ARRAY[@]}" >&2
+  #printf "\n" >&2
+
+  # Get all combinations
+  for (( i=0; i<${#IDX_ARRAY[@]}-1; i++ ))
+  do
+    A=${IDX_ARRAY[i]}
+    for (( j=i+1; j<${#IDX_ARRAY[@]}; j++ ))
+    do
+      B=${IDX_ARRAY[j]}
+      DIFF=$(( B - A ))
+      VDIFF=$(( (B / LEN) - (A / LEN) ))
+      # Assign heads
+      HEADC=1
+      while true
+      do
+        HEAD=$(( A - DIFF * HEADC ))
+	HEADVDIFF=$(( ( (A / LEN) - (HEAD / LEN) ) / HEADC ))
+        # Check if out of bounds
+        if [[ $HEAD -lt ${#MAP_ARRAY[@]} ]] && \
+           [[ $HEAD -ge 0 ]] && \
+           [[ $HEADVDIFF -eq $VDIFF ]]
+        then
+          SHADOW_ARRAY[HEAD]=X # Mark on shadow map
+	  (( HEADC++ ))
+        else
+          break
+        fi
+      done
+      # Assign tails
+      TAILC=1
+      while true
+      do
+        TAIL=$(( B + DIFF * TAILC ))
+	TAILVDIFF=$(( ( (TAIL / LEN) - (B / LEN) ) / TAILC ))
+        # Check if out of bounds
+        if [[ $TAIL -lt ${#MAP_ARRAY[@]} ]] && \
+           [[ $TAIL -ge 0 ]] && \
+           [[ $TAILVDIFF -eq $VDIFF ]]
+        then
+          SHADOW_ARRAY[TAIL]=X # Mark on shadow map
+	  (( TAILC++ ))
+        else
+          break
+        fi
+      done
+      #printf "char: %s, A: %s, B: %s, DIFF: %s, VDIFF: %s, HEAD: %s, HEADVDIFF: %s, TAIL: %s, TAILVDIFF: %s\n"  "$CHAR" "$A" "$B" "$DIFF" "$VDIFF" "$HEAD" "$HEADVDIFF" "$TAIL" "$TAILVDIFF" >&2
+    done
+  done
+  unset IDX_ARRAY
+
+done
+printf "%s" "${SHADOW_ARRAY[@]}" | fold -w "$LEN" | sed -E 's/(.)/\1\ /g'
+printf "\n"
+printf "%s" "${SHADOW_ARRAY[@]}" | grep -o 'X' | wc -l