feat: adding RootingTreeFromGraph algorithm.

Author: dkunz2024

Trees/RootingTreeFromGraph.js

@@ -0,0 +1,59 @@
+/*
+* Author: Denton Kunz
+* Tree rooting algorithm in Javascript
+* Takes in an undirected graph (adjacency matrix)
+* Follows pseudocode given at https://youtu.be/2FFq2_je7Lg?si=rIwT8UCYcaGhxH6h
+* Node class can be modified to include a data field
+*/
+
+class Node {
+    constructor(id, parent, children=[]){
+        this.id = id
+        this.parent = parent
+        this.children = children
+    }
+}
+
+function rootTree(graph, rootId=0){
+
+    console.log(graph)
+
+    //the first node (root) should start with no parents/children
+    const root = new Node(rootId, null)
+    //recursively generate the rest of the tree
+    return buildTree(graph, root, null)
+}
+
+function buildTree(graph, node, parent){
+    //let i represent the id of the child node
+    for (let i = 0; i < graph[node.id].length; i++) {
+        //skip until we find a child node
+        if(graph[node.id][i]==0){
+            // console.log("skipped 1")
+            continue
+        }
+
+        //if the child node is the current node, skip this case
+        if(node.id == i){
+            // console.log("skipped 2")
+            continue
+        }
+
+        //avoid creating an edge between child and the current node's parent
+        if( parent != null && i == parent.id){
+            // console.log("skipped 3")
+            continue
+        }
+
+        //create and add the new node
+        let child = new Node(i, node)
+        node.children.push(child)
+
+        //recursively iterate using that node
+        buildTree(graph, child, node)
+    }
+
+    return node
+}
+
+export {Node, rootTree, buildTree}

Trees/test/RootingTreeFromGraph.test.js

@@ -0,0 +1,29 @@
+import {rootTree} from '../RootingTreeFromGraph'
+
+describe('Test 1', () =>{
+    /* Graph structure:
+    *
+    *   0      3 - 4
+    *     \   /
+    *       1
+    *      /
+    *     2
+    */
+    const myGraph = [[1,1,0,0,0],
+                    [1,1,1,1,0],
+                    [0,1,1,0,0],
+                    [0,1,0,1,1],
+                    [0,0,0,1,1]]
+
+    it('testing', () => {
+        const res = rootTree(myGraph)
+        expect(res.id).toStrictEqual(0)
+        expect(res.children.length).toStrictEqual(1)
+        expect(res.children[0].id).toStrictEqual(1)
+        expect(res.children[0].children.length).toStrictEqual(2)
+        expect(res.children[0].children[0].id).toStrictEqual(2)
+        expect(res.children[0].children[1].id).toStrictEqual(3)
+        expect(res.children[0].children[1].children.length).toStrictEqual(1)
+        expect(res.children[0].children[1].children[0].id).toStrictEqual(4)
+    })
+})