- Added more guest contributions by Laurent Rosenfeld.

4 files changed, 108 insertions, 0 deletions

diff --git a/challenge-174/laurent-rosenfeld/javascript/ch-2.js b/challenge-174/laurent-rosenfeld/javascript/ch-2.js
new file mode 100644
index 0000000000..c943830310
--- /dev/null
+++ b/challenge-174/laurent-rosenfeld/javascript/ch-2.js
@@ -0,0 +1,34 @@
+function permute(inputArray) {
+    let inAry = [...inputArray].sort(); //copy and sort input
+    return inAry.reduce(function permute(res, item, key, arr) {
+        return res.concat(arr.length > 1 && arr.slice(0, key)
+            .concat(arr.slice(key + 1))
+            .reduce(permute, [])
+            .map(function (perm) {
+                 return [item].concat(perm);
+            }) || item);
+    }, []);
+}
+
+function permutation2rank(perms, in_perm) {
+    let input = JSON.stringify(in_perm)
+    for (var i = 0; i < perms.length; i++) {
+        // stringify permutations to enable comparison
+        if (JSON.stringify(perms[i]) == input) {
+            return i
+        }
+    }
+}
+
+function rank2permutation(perm_list, index) {
+    return perm_list[index]
+}
+
+let perm_in = [3, 1, 2];
+let perms = permute(perm_in)
+console.log(perms)
+let rank = permutation2rank(perms, perm_in)
+console.log("Permutation", perm_in, "has rank", rank)
+for (var i = 0; i < perms.length; i++) {
+    console.log("Rank: ", i, " -> permutation ", rank2permutation(perms, i))
+}
diff --git a/challenge-174/laurent-rosenfeld/julia/ch-2.jl b/challenge-174/laurent-rosenfeld/julia/ch-2.jl
new file mode 100644
index 0000000000..704124f860
--- /dev/null
+++ b/challenge-174/laurent-rosenfeld/julia/ch-2.jl
@@ -0,0 +1,26 @@
+# Note: Julia array subscripts start at 1, not 0
+using Combinatorics
+
+function permute(in_list)
+    return collect(permutations(sort(in_list), length(in_list)))
+end
+
+function permutation2rank(perms, input)
+    for i in 1:length(perms)
+        if perms[i] == input
+            return i
+        end
+    end
+end
+
+function rank2permutation(perm_list, index)
+    return perm_list[index]
+end
+
+perm_in = [3, 1, 2]
+perms = permute(perm_in)
+println("Permutations: ", perms)
+println("Permutation ", perm_in, " -> rank ", permutation2rank(perms, perm_in))
+for i in 1:length(perms)
+    println("Rank: ", i, " -> permutation ", rank2permutation(perms, i))
+end
diff --git a/challenge-174/laurent-rosenfeld/python/ch-2.py b/challenge-174/laurent-rosenfeld/python/ch-2.py
new file mode 100644
index 0000000000..c472dd0db0
--- /dev/null
+++ b/challenge-174/laurent-rosenfeld/python/ch-2.py
@@ -0,0 +1,25 @@
+def stringify(input):
+  return " ".join(map(str, input))
+
+def permute(input):
+  temp = input.copy() # avoid modifying input perm with the sort
+  temp.sort()
+  return list(itertools.permutations(temp))
+
+def permutation2rank(perms, input):
+  perms_str = map(stringify, perms)
+  input_str = stringify(input)
+  for index, value in enumerate(perms_str):
+    if value == input_str:
+      return index
+
+def rank2permutation(permutation, rank):
+  return permutation[rank]
+
+perm = [3, 1, 2]
+perms = permute(perm)
+print("Permutations: ", str(perms))
+rank = permutation2rank(perms, perm)
+print("Permutation ", perm, " -> rank ", rank)
+for i in range(0, len(perms)):
+  print("Rank: ", i, " -> permutation ", rank2permutation(perms, i))
diff --git a/challenge-174/laurent-rosenfeld/ruby/ch-2.rb b/challenge-174/laurent-rosenfeld/ruby/ch-2.rb
new file mode 100644
index 0000000000..e2fea01378
--- /dev/null
+++ b/challenge-174/laurent-rosenfeld/ruby/ch-2.rb
@@ -0,0 +1,23 @@
+def permute(in_list)
+    return in_list.sort.permutation(in_list.length).to_a
+end
+
+def permutation2rank(perms, input)
+    for i in 0..perms.length - 1
+        if perms[i] == input
+            return i
+        end
+    end
+end
+
+def rank2permutation(perms, index)
+    return perms[index]
+end
+
+perm_in = [3, 1, 2]
+perms = permute(perm_in)
+puts("Permutations: #{perms} \n")
+print("Permutation #{perm_in} -> rank  #{permutation2rank(perms, perm_in)} \n")
+for i in 1..perms.length - 1
+    print("Rank:  #{i} -> permutation  #{rank2permutation(perms, i)} \n")
+end