day03/diag.sh

   1 #!/bin/bash
   2
   3 set -e
   4 set -u
   5
   6 filename="${1:-example.txt}"
   7
   8 exec 3<"$filename"
   9
  10 line_length=0
  11 declare -a most_common=( 0 )
  12 declare -a all_binaries
  13 line_count=0
  14
  15 while read -u 3 line; do
  16     all_binaries+=($line)
  17     if [ $line_length -eq 0 ]; then
  18         line_length=${#line}
  19     fi
  20     for (( i=0; i < $line_length; i++ )); do
  21         if [ ${#most_common[@]} -lt $i ]; then
  22             most_common[$i]=0
  23         fi
  24         if [ ${line:$i:1} -eq 1 ]; then
  25             ((most_common[$i]+=1))
  26         fi
  27     done
  28     ((line_count+=1))
  29 done
  30
  31 half_line_count=$((line_count/2))
  32 binary_string=""
  33 inverse_binary_string=""
  34
  35 for (( i=0; i < $line_length; i++ )); do
  36     if [ ${most_common[$i]} -gt $half_line_count ]; then
  37         binary_string+=1
  38         inverse_binary_string+=0
  39     else
  40         binary_string+=0
  41         inverse_binary_string+=1
  42     fi
  43 done
  44
  45 total=$((2#$binary_string * 2#$inverse_binary_string))
  46
  47 echo Answer: $total
  48
  49 declare -a co2_scrubber
  50 declare -a o2_generator
  51
  52 # first populate co2_scrubbers and o2_generator
  53
  54 co2_filter_digit=1
  55 o2_generator_digit=0
  56
  57 if [ ${most_common[0]} -gt $half_line_count ]; then
  58     co2_filter_digit=0
  59     o2_generator_digit=1
  60 else
  61     co2_filter_digit=1
  62     o2_generator_digit=0
  63 fi
  64
  65 for val in "${all_binaries[@]}"; do
  66     if [ ${val:0:1} -eq $co2_filter_digit ]; then
  67         co2_scrubber+=($val)
  68     fi
  69     if [ ${val:0:1} -eq $o2_generator_digit ]; then
  70         o2_generator+=($val)
  71     fi
  72 done
  73
  74 get_most_common() {
  75     offset=$1
  76     local -n arr=$2
  77     ones=0
  78     zeros=0
  79
  80     for val in "${arr[@]}"; do
  81         part=${val:$offset:1}
  82         if [ $part -eq 1 ]; then
  83             ((ones+=1))
  84         else
  85             ((zeros+=1))
  86         fi
  87     done
  88
  89     if [ $ones -gt $zeros ]; then
  90         echo 1
  91     elif [ $ones -lt $zeros ]; then
  92         echo 0
  93     else
  94         echo 2
  95     fi
  96 }
  97
  98 get_least_common() {
  99     offset=$1
 100     array_name=$2
 101
 102     val=$(get_most_common $offset $array_name)
 103     case $val in
 104         0)
 105             echo 1
 106             ;;
 107         1)
 108             echo 0
 109             ;;
 110         2)
 111             echo 2
 112             ;;
 113     esac
 114 }
 115
 116 filter_array() {
 117     val=$1
 118     pos=$2
 119     local -n arr=$3
 120
 121     if [ ${#arr[@]} -eq 1 ]; then
 122         return
 123     fi
 124
 125     declare -a new_arr
 126     for thing in "${arr[@]}"; do
 127         if [ ${thing:$pos:1} -eq $val ]; then
 128             new_arr+=($thing)
 129         fi
 130     done
 131
 132     arr=("${new_arr[@]}")
 133 }
 134
 135 for ((i=1; i < $line_length; i++)); do
 136     co2_filter=$(get_least_common $i co2_scrubber)
 137     o2_filter=$(get_most_common $i o2_generator)
 138
 139     if [ $co2_filter -eq 2 ]; then
 140         co2_filter=0
 141     fi
 142
 143     if [ $o2_filter -eq 2 ]; then
 144         o2_filter=1
 145     fi
 146
 147     filter_array $co2_filter $i co2_scrubber
 148     filter_array $o2_filter $i o2_generator
 149 done
 150
 151 # we've only got 1 in each - so...
 152 echo Life Support Rating: $((2#${o2_generator[0]} * 2#${co2_scrubber[0]}))