Day 13 added, bash & C.

day13/ex2.bash

@@ -0,0 +1,32 @@
+#!/bin/bash
+#
+# ex1.bash: Advent2020 game, day 13/game 2.
+
+CMD=${0##*/}
+shopt -s extglob
+
+declare -a buses btimes
+declare -i lcm=1 thetime=0 c=0 t=0
+
+read -r line
+read -r line
+IFS=,
+for i in ${line}; do
+	if [[ $i != x ]]; then
+		buses[$c]=$i
+		btimes[$c]=$t
+		((c++))
+	fi
+	((t++))
+done
+for ((i=0; i<(${#buses[@]}-1); ++i)); do
+	bus=${buses[i+1]}
+	idx=${btimes[i+1]}
+	((lcm*=buses[i]))
+	while ((((thetime + idx) % bus) != 0)); do
+		((thetime+=lcm))
+	done
+
+done
+printf "%s : res=%d\n" "$CMD" "$thetime"
+exit 0