Bash solution for week 100, part 2

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diff --git a/challenge-100/abigail/bash/ch-2.sh b/challenge-100/abigail/bash/ch-2.sh
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+#!/bin/sh
+
+#
+# See ../README.md
+#
+
+#
+# Run as: bash ch-2.sh < input-file
+#
+
+set -f
+
+#
+# Bash only has one-dimensional arrays, so we're using a function
+# to map 2-d indices to a 1-d index.
+#
+# Note also that we can only return numbers 0 - 255 as "return" values
+# (by hijacking the return status), which isn't good enough for us,
+# so we use the global variable "index" to pass the result back.
+#
+
+function idx () {
+    local x=$1
+    local y=$2
+    index=$((x * (x + 1) / 2 + y))
+}
+
+#
+# Read in the data: we can read a line at the time, and have
+# it split on white space, giving use an array of numbers in "row".
+# We iterate over the row, mapping the x, y coordinates to a
+# single index, and storing the result in the array "numbers".
+#
+
+x=0
+while read -a row
+do    for  ((y = 0; y < ${#row[*]}; y ++))
+      do   idx $x $y
+           numbers[$index]=${row[$y]}
+      done
+      x=$((x + 1))
+done
+
+#
+# Work bottom to top to calculate the minimum path.
+#
+for  ((r = $x - 2; r >= 0; r --))
+do   for  ((y = 0; y <= $r; y ++))
+     do   idx $((r + 1)) $y
+          val1=${numbers[$index]}
+          idx $((r + 1)) $((y + 1))
+          val2=${numbers[$index]}
+          min=$((val1 < val2 ? val1 : val2))
+          idx $r $y
+          numbers[$index]=$((numbers[$index] + $min))
+     done
+done
+
+
+#
+# Print the result.
+#
+echo ${numbers[0]}