add part1 and data

day/02/demo_2_input.txt

@@ -0,0 +1,4 @@
+1 3 5 6
+1 2 3 99
+1 3 2 3
+9 8 9 10

day/02/demo_input.txt

@@ -0,0 +1,6 @@
+7 6 4 2 1
+1 2 7 8 9
+9 7 6 2 1
+1 3 2 4 5
+8 6 4 4 1
+1 3 6 7 9

day/02/part1.sh

@@ -0,0 +1,66 @@
+#! /bin/bash
+
+#set -x
+
+FILE_IN="${1}"
+
+safe_count=0
+
+while read -r l; do
+  echo "reading new line [$l]"
+
+  IFS=" "
+  read -ra line_split <<< "${l}"
+  unset IFS
+
+  # start with the first val
+  prev_val="${line_split[0]}"
+
+  is_safe=1
+
+  # if positive, going up, if negative, going down!
+  is_up_down="$((line_split[1] - line_split[0]))"
+
+  if [[ "${is_up_down}" -ge 0 ]]; then
+    echo "Initially going up"
+  else
+    echo "Initially going down"
+  fi
+
+  for v in "${line_split[@]:1}"; do
+    echo "checking [${v}] against previous [${prev_val}]"
+    prev_diff=$((v - prev_val))
+    echo "diff ${prev_diff}"
+
+
+    if [[ "${prev_diff}" -gt 0 ]]; then
+      echo "going up"
+      if [[ "${is_up_down}" -le 0 ]]; then
+        echo "wrong direction"
+        is_safe=0
+      fi
+    else
+      echo "going down"
+      if [[ "${is_up_down}" -ge 0 ]]; then
+        echo "wrong direction"
+        is_safe=0
+      fi
+    fi
+
+    if [[ "${prev_diff#-}" -le 0 ]] || [[ "${prev_diff#-}" -ge 4 ]]; then
+      echo "outside range"
+      is_safe=0
+    fi
+
+    if [[ "${is_safe}" -ne 0 ]]; then
+      echo "safe"
+    else
+      echo "unsafe"
+    fi
+    prev_val=$v
+  done
+
+  safe_count=$((safe_count + is_safe))
+done <"$FILE_IN"
+
+echo "final safe count ${safe_count}"