Added solution to ch4-3 and associated tests.

Author: diadical

src/chapter4/ch4-q03.js

@@ -0,0 +1,29 @@
+'use strict';
+import { LinkedList } from './helpers';
+
+/**
+ * Travels through tree and adds values into a list of linked lists. Each level
+ * of tree is represented in a linked list.
+ *
+ * N = |tree|
+ * Time: O(N)
+ * Additional space: O(N)
+ */
+export function listTreeByDepthOrder(tree) {
+  let lists = [];
+  addToList(lists, tree.root, 0);
+  return lists;
+}
+
+function addToList(lists, node, depth) {
+  if (node) {
+    if (!lists[depth]) {
+      lists[depth] = new LinkedList();
+    }
+
+    lists[depth].append(node.val);
+
+    addToList(lists, node.left, depth + 1);
+    addToList(lists, node.right, depth + 1);
+  }
+}

src/chapter4/ch4-q03.spec.js

@@ -0,0 +1,80 @@
+import { expect } from 'chai';
+import * as helpers from './helpers';
+import * as funcs from './ch4-q03';
+
+function toArrayOfArrays(lists) {
+  return lists.map(l => l.toArray());
+}
+
+for (let key in funcs) {
+  let func = funcs[key];
+
+  describe('ch4-q03: ' + key, function() {
+
+    beforeEach(function() {
+      this.tree = new helpers.Tree();
+    });
+
+    it('returns empty list for empty tree', function() {
+      expect(toArrayOfArrays(func(this.tree))).to.eql([]);
+    });
+
+    it('returns true for single node tree', function() {
+      this.tree.add(10);
+      expect(toArrayOfArrays(func(this.tree))).to.eql([[10]]);
+    });
+
+    it('returns single value lists for left heavy tree', function() {
+      [10, 9, 8].forEach(v => this.tree.add(v));
+      expect(toArrayOfArrays(func(this.tree))).to.eql([
+        [10],
+        [9],
+        [8]
+      ]);
+    });
+
+    it('returns 2 value lists for upside down V shaped tree', function() {
+      [10, 11, 12, 13, 9, 8, 7].forEach(v => this.tree.add(v));
+      expect(toArrayOfArrays(func(this.tree))).to.eql([
+        [10],
+        [9, 11],
+        [8, 12],
+        [7, 13]
+      ]);
+    });
+
+    it('returns true for larger balanced tree', function() {
+      let expected = [];
+      this.tree.add(8);
+      expected.push([8]);
+      expect(toArrayOfArrays(func(this.tree)), 'root').to.be.eql(expected);
+      this.tree.add(4);
+      this.tree.add(12);
+      expected.push([4, 12]);
+      expect(toArrayOfArrays(func(this.tree)), 'depth 1').to.eql(expected);
+      this.tree.add(2);
+      this.tree.add(6);
+      this.tree.add(10);
+      this.tree.add(14);
+      expected.push([2, 6, 10, 14]);
+      expect(toArrayOfArrays(func(this.tree)), 'depth 2').to.eql(expected);
+      this.tree.add(1);
+      this.tree.add(3);
+      this.tree.add(5);
+      this.tree.add(7);
+      expected.push([1, 3, 5, 7]);
+      expect(toArrayOfArrays(func(this.tree)), '1/2 depth 3').to.eql(expected);
+      this.tree.add(9);
+      this.tree.add(11);
+      this.tree.add(13);
+      this.tree.add(15);
+      expected[expected.length - 1].push(9, 11, 13, 15);
+      expect(toArrayOfArrays(func(this.tree)), 'depth 3').to.eql(expected);
+      this.tree.add(16);
+      expected.push([16]);
+      expect(toArrayOfArrays(func(this.tree)), '1 depth 4').to.eql(expected);
+    });
+
+  });
+
+}