Data commit

Task/Dutch-national-flag-problem/UNIX-Shell/dutch-national-flag-problem-1.sh

@@ -0,0 +1,58 @@
+COLORS=(red white blue)
+
+# to go from name to number, we make variables out of the color names
+# (e.g. the variable "$red" has value "1").
+for (( i=0; i<${#COLORS[@]}; ++i )); do
+  eval ${COLORS[i]}=$i
+done
+
+# Make a random list
+function random_balls {
+  local -i n="$1"
+  local -i i
+  local balls=()
+  for (( i=0; i < n; ++i )); do
+    balls+=("${COLORS[RANDOM%${#COLORS[@]}]}")
+  done
+  echo "${balls[@]}"
+}
+
+# Test for Dutchness
+function dutch? {
+  if (( $# < 2 )); then
+     return 0
+  else
+    local first="$1"
+    shift
+    if eval "(( $first > $1 ))"; then
+      return 1
+    else
+      dutch? "$@"
+    fi
+  fi
+}
+
+# Sort into order
+function dutch {
+  local -i lo=-1 hi=$# i=0
+  local a=("$@")
+  while (( i < hi )); do
+    case "${a[i]}" in
+      red)
+        let lo+=1
+        local t="${a[lo]}"
+        a[lo]="${a[i]}"
+        a[i]="$t"
+        let i+=1
+        ;;
+      white) let i+=1;;
+      blue)
+        let hi-=1
+        local t="${a[hi]}"
+        a[hi]="${a[i]}"
+        a[i]="$t"
+        ;;
+    esac
+  done
+  echo "${a[@]}"
+}

Task/Dutch-national-flag-problem/UNIX-Shell/dutch-national-flag-problem-2.sh

@@ -0,0 +1,8 @@
+declare -i len=${1:-10}
+balls=()
+while (( ${#balls[@]} < len )) || dutch? "${balls[@]}"; do
+  balls=($(random_balls "$len"))
+done
+echo "Initial list: ${balls[@]}"
+balls=($(dutch "${balls[@]}"))
+echo "Sorted: ${balls[@]}"