Data commit

Task/Permutations/UNIX-Shell/permutations-1.sh

@@ -0,0 +1,27 @@
+function permute {
+  if (( $# == 1 )); then
+    set -- $(seq $1)
+  fi
+  local A=("$@")
+  permuteAn "$#"
+}
+
+function permuteAn {
+  # print all permutations of first n elements of the array A, with remaining
+  # elements unchanged.
+  local -i n=$1 i
+  shift
+  if (( n == 1 )); then
+    printf '%s\n' "${A[*]}"
+  else
+    permuteAn $(( n-1 ))
+    for (( i=0; i<n-1; ++i )); do
+      local -i k
+      (( k=n%2 ? 0: i ))
+      local t=${A[k]}
+      A[k]=${A[n-1]}
+      A[n-1]=$t
+      permuteAn $(( n-1 ))
+    done
+  fi
+}

Task/Permutations/UNIX-Shell/permutations-2.sh

@@ -0,0 +1,19 @@
+function permuteAn {
+  # print all permutations of first n elements of the array A, with remaining
+  # elements unchanged.
+  local -i n=$1 i
+  shift
+  if (( n == 1 )); then
+    printf '%s\n' "${A[*]}"
+  else
+    permuteAn $(( n-1 ))
+    for (( i=1; i<n; ++i )); do
+      local -i k
+      (( k=n%2 ? 1 : i ))
+      local t=$A[k]
+      A[k]=$A[n]
+      A[n]=$t
+      permuteAn $(( n-1 ))
+    done
+  fi
+}