From 8c47bd0020101f64614229cbae7ea991720a6199 Mon Sep 17 00:00:00 2001
From: chirvasitua <stuart-little@users.noreply.github.com>
Date: Tue, 20 Apr 2021 17:58:38 -0400
Subject: 1st commit on 109_node

---
 challenge-109/stuart-little/node/ch-1.js |  5 +++
 challenge-109/stuart-little/node/ch-2.js | 72 ++++++++++++++++++++++++++++++++
 2 files changed, 77 insertions(+)
 create mode 100755 challenge-109/stuart-little/node/ch-1.js
 create mode 100755 challenge-109/stuart-little/node/ch-2.js

diff --git a/challenge-109/stuart-little/node/ch-1.js b/challenge-109/stuart-little/node/ch-1.js
new file mode 100755
index 0000000000..4473ce70c0
--- /dev/null
+++ b/challenge-109/stuart-little/node/ch-1.js
@@ -0,0 +1,5 @@
+#!/usr/bin/env node
+
+// run <script>
+
+console.log("0, 0, 0, 2, 0, 5, 0, 6, 3, 7, 0, 15, 0, 9, 8, 14, 0, 20, 0, 21");
diff --git a/challenge-109/stuart-little/node/ch-2.js b/challenge-109/stuart-little/node/ch-2.js
new file mode 100755
index 0000000000..52af5408a8
--- /dev/null
+++ b/challenge-109/stuart-little/node/ch-2.js
@@ -0,0 +1,72 @@
+#!/usr/bin/env node
+
+// run <script> <space-separated numbers>
+
+/*
+Heap's algorithm for generating permutations
+
+Refs:
+
+[0] https://stackoverflow.com/a/37580979/11064961
+[1] https://en.m.wikipedia.org/wiki/Heap's_algorithm
+*/
+
+function permute(arr) {
+  let length = arr.length,
+      result = [arr.slice()],
+      c = new Array(length).fill(0),
+      i = 1, k, p;
+
+  while (i < length) {
+    if (c[i] < i) {
+      k = i % 2 && c[i];
+      p = arr[i];
+      arr[i] = arr[k];
+      arr[k] = p;
+      ++c[i];
+      i = 1;
+      result.push(arr.slice());
+    } else {
+      c[i] = 0;
+      ++i;
+    }
+  }
+  return result;
+}
+
+Array.prototype.sum = function () {
+    return this.reduce((acc,val) => acc + val, 0)
+}
+
+function checkAllSumsEqNr(nr,ar,bl) {
+    if (ar.length <= 3) {
+	return (nr == ar.sum()) && bl
+    };
+    return checkAllSumsEqNr(
+	nr,
+	ar.slice(2),
+	(nr == ar.slice(0,3).sum()) && bl
+    )
+};
+
+function allSumsEq(ar) {
+    if (ar.length <= 2) {
+	return true;
+    };
+    return checkAllSumsEqNr(
+	ar.slice(0,2).sum(),
+	ar.slice(1),
+	true
+    )
+}; 
+
+function pprnt(ar) {
+    const sm = ar.slice(0,2).sum();
+    const lettersId = ar.map((v,i) => `${String.fromCharCode(97+i)} = ${ar[i]}`).join(", ");
+    return `\nSolution: ${lettersId}\nSum: ${sm}`;
+}
+
+const inpt = process.argv.slice(2).map(x => parseInt(x,10));
+const sols = permute([...inpt]).filter(allSumsEq);
+
+console.log((sols.length == 0) ? ("No solution.") : (sols.map(pprnt).join("\n")));
-- 
cgit