improve(findset): add new member func 'initNode' to init a specify node in the findset

Author: guanghechen

Diff for: packages/findset/__test__/findset.spec.ts

@@ -31,6 +31,11 @@ describe('createfindset', function () {
     expect(findset.root(2)).toBe(findset.root(3))
 
     for (let i = 4; i <= MAX_N; ++i) expect(findset.root(i)).toBe(i)
+
+    findset.initNode(2)
+    findset.initNode(3)
+    expect(findset.root(2)).toBe(2)
+    expect(findset.root(3)).toBe(3)
   })
 
   test('out of boundary', function () {
@@ -69,6 +74,13 @@ describe('createHeuristicfindset', function () {
     expect(findset.root(2)).toBe(findset.root(3))
 
     for (let i = 4; i <= MAX_N; ++i) expect(findset.root(i)).toBe(i)
+
+    findset.initNode(2)
+    findset.initNode(3)
+    expect(findset.root(2)).toBe(2)
+    expect(findset.size(2)).toBe(1)
+    expect(findset.root(3)).toBe(3)
+    expect(findset.size(3)).toBe(1)
   })
 
   test('out of boundary', function () {

Diff for: packages/findset/src/enhanced.ts

@@ -14,18 +14,13 @@ import type { Findset } from './ordinary'
  *  findset.merge(2)
  */
 export interface EnhancedFindset extends Findset {
-  /**
-   *
-   * @param x
-   */
-  initNode(x: number): void
   /**
    * Size (number of the nodes) of the tree which x belongs.
    * @param x
    */
   size(x: number): number
   /**
-   *
+   * Get the set which contains all nodes of the tree which x belongs.
    * @param x
    */
   getSetOf(x: number): Readonly<Set<number>> | undefined

Diff for: packages/findset/src/heuristic.ts

@@ -26,7 +26,7 @@ export function createHeuristicFindset(): HeuristicFindset {
   const count: number[] = []
 
   let _size = 0
-  return { init, root, merge, size }
+  return { init, initNode, root, merge, size }
 
   function init(N: number): void {
     _size = N
@@ -38,6 +38,11 @@ export function createHeuristicFindset(): HeuristicFindset {
     }
   }
 
+  function initNode(x: number): void {
+    parent[x] = x
+    count[x] = 1
+  }
+
   function root(x: number): number | never {
     if (x < 1 || x > _size)
       throw new RangeError(`Out of boundary [1, ${_size}]. x: ${x}`)

Diff for: packages/findset/src/ordinary.ts

@@ -14,10 +14,15 @@
  */
 export interface Findset {
   /**
-   * Initialize the findSet.
+   * Initialize the findset .
    * @param N
    */
   init(N: number): void
+  /**
+   * Initialize a specified node in the findset.
+   * @param x
+   */
+  initNode(x: number): void
   /**
    * Find the root element of x.
    * @param x
@@ -39,14 +44,18 @@ export interface Findset {
 export function createFindset(): Findset {
   const parent: number[] = []
   let _size = 0
-  return { init, root, merge }
+  return { init, initNode, root, merge }
 
   function init(N: number): void {
     _size = N
     if (parent.length <= _size) parent.length = _size + 1
     for (let i = 1; i <= N; ++i) parent[i] = i
   }
 
+  function initNode(x: number): void {
+    parent[x] = x
+  }
+
   function root(x: number): number {
     if (x < 1 || x > _size)
       throw new RangeError(`Out of boundary [1, ${_size}]. x: ${x}`)