rename repo, subdir for yearly challenges

2020/day09/ex1.bash

@@ -0,0 +1,51 @@
+#!/bin/bash
+#
+# ex1.bash: Advent2020 game, day 9/game 1.
+
+CMD=${0##*/}
+shopt -s extglob
+
+declare -i N=5 SIZE
+declare -a LIST=()
+
+function push25 () {
+	local i
+	for ((i=0; i<25; ++i)); do
+		read -r i
+		LIST+=("$i")
+	done
+}
+
+function push() {
+	local i
+	while read -r i; do
+		LIST+=("$i")
+	done
+	SIZE=${#LIST[@]}
+}
+
+function badnum() {
+	local -i cur="$1" i j
+	local -i res=${LIST[$cur]}
+	local -i start=$((cur-N-1))
+	for ((i=start; i<cur; ++i)); do
+		for ((j=i+1; j<cur; ++j)); do
+			if (((LIST[i]+LIST[j]) == res)); then
+				return 0
+			fi
+		done
+	done
+	return 1
+}
+[[ $# = 1 ]] && N=$1
+
+push
+declare -i i target
+for ((i=N; i<SIZE; ++i)); do
+	badnum $i || break
+done
+target="${LIST[$i]}"
+
+printf "%s : res=%d\n" "$CMD" "$target"
+
+exit 0