rename repo, subdir for yearly challenges

2020/day03/ex2.bash

@@ -0,0 +1,31 @@
+#!/bin/bash
+#
+# ex1.bash: Advent2020 game, day 3/game 2.
+
+CMD=${0##*/}
+
+XMOVES=(1 3 5 7 1)								  # moves right
+YMOVES=(1 1 1 1 2)								  # moves down
+declare -i linelen=0 modpos=0 res=1 ypos=1
+declare -a xpos xcount
+
+read -r line									  # ignore 1st line
+
+while read -r line; do
+	(( ypos++ ))
+	(( linelen = ${#line} ))
+
+	for ((i=0; i<${#XMOVES[@]}; ++i)); do
+		if ((ypos % YMOVES[i] == 0)); then
+			(( xpos[i] += XMOVES[i] ))			  # move right
+			(( modpos = (xpos[i] % linelen) ))
+			[[ ${line:modpos:1} = \# ]] && ((xcount[i]++))
+		fi
+	done
+done
+
+for ((i=0; i<${#XMOVES[@]}; ++i)); do
+	(( res *= xcount[i] ))
+done
+printf "%s : lines=%d res=%d\n " "$CMD" $ypos $res
+exit 0