From 024c82ff92b0b9a708920591d3eb0ac066164014 Mon Sep 17 00:00:00 2001
From: Alexander Rose <alex.rose@rcsb.org>
Date: Fri, 27 Jul 2018 09:51:47 -0700
Subject: [PATCH] added combination iterator
---
src/mol-data/util/_spec/combination.spec.ts | 29 +++++++++
src/mol-data/util/combination.ts | 65 +++++++++++++++++++++
2 files changed, 94 insertions(+)
create mode 100644 src/mol-data/util/_spec/combination.spec.ts
create mode 100644 src/mol-data/util/combination.ts
diff --git a/src/mol-data/util/_spec/combination.spec.ts b/src/mol-data/util/_spec/combination.spec.ts
new file mode 100644
index 000000000..a11c12f84
--- /dev/null
+++ b/src/mol-data/util/_spec/combination.spec.ts
@@ -0,0 +1,29 @@
+/**
+ * Copyright (c) 2018 mol* contributors, licensed under MIT, See LICENSE file for more info.
+ *
+ * @author Alexander Rose <alexander.rose@weirdbyte.de>
+ */
+
+import { combinations } from '../combination'
+
+describe('Combination', () => {
+ it('test123-2', () => {
+ const c = combinations([1, 2, 3], 2)
+ expect(c).toEqual([[1, 2], [1, 3], [2, 3]]);
+ });
+
+ it('test1234-2', () => {
+ const c = combinations([1, 2, 3, 4], 2)
+ expect(c).toEqual([[1, 2], [1, 3], [2, 3], [1, 4], [2, 4], [3, 4]]);
+ });
+
+ it('test1234-1', () => {
+ const c = combinations([1, 2, 3, 4], 1)
+ expect(c).toEqual([[1], [2], [3], [4]]);
+ });
+
+ it('test1234-4', () => {
+ const c = combinations([1, 2, 3, 4], 4)
+ expect(c).toEqual([[1, 2, 3, 4]]);
+ });
+});
\ No newline at end of file
diff --git a/src/mol-data/util/combination.ts b/src/mol-data/util/combination.ts
new file mode 100644
index 000000000..d37a23eec
--- /dev/null
+++ b/src/mol-data/util/combination.ts
@@ -0,0 +1,65 @@
+/**
+ * Copyright (c) 2018 mol* contributors, licensed under MIT, See LICENSE file for more info.
+ *
+ * @author Alexander Rose <alexander.rose@weirdbyte.de>
+ */
+
+// adpated from https://github.com/dankogai/js-combinatorics, MIT 2013-2016 Dan Kogai
+
+import Iterator from '../iterator'
+
+function P(m: number, n: number) {
+ let p = 1
+ while (n--) p *= m--
+ return p
+}
+
+function C(m: number, n: number) {
+ if (n > m) return 0
+ return P(m, n) / P(n, n)
+}
+
+function nextIndex(n: number) {
+ const smallest = n & -n
+ const ripple = n + smallest
+ const newSmallest = ripple & -ripple
+ const ones = ((newSmallest / smallest) >> 1) - 1
+ return ripple | ones
+};
+
+export class CombinationIterator<T> implements Iterator<T[]> {
+ private value: T[]
+ private index: number
+ private maxIndex: number
+
+ size: number
+ hasNext: boolean = false;
+
+ move() {
+ if (this.hasNext) {
+ let i = 0, j = 0, n = this.index
+ for (; n; n >>>= 1, i++) {
+ if (n & 1) this.value[j++] = this.array[i]
+ }
+ this.index = nextIndex(this.index)
+ this.hasNext = this.index < this.maxIndex
+ }
+ return this.value;
+ }
+
+ constructor(private array: T[], count: number) {
+ this.index = (1 << count) - 1
+ this.size = C(array.length, count)
+ this.maxIndex = 1 << array.length,
+
+ this.value = new Array(count)
+ this.hasNext = count > 0 && count <= array.length
+ }
+}
+
+export function combinations<T>(array: T[], count: number): T[][] {
+ const out: T[][] = []
+ const combinationIt = new CombinationIterator(array, count)
+ while (combinationIt.hasNext) out.push(combinationIt.move().slice())
+ return out
+}
\ No newline at end of file
--
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