feat(treeMap): get last entry (highest value)

Author: amejiarosario

src/data-structures/maps/tree-maps/tree-map.js

@@ -18,6 +18,11 @@ const Tree = require('../../trees/red-black-tree'); // fast insertion
  *        allocate memory beforehand (e.g. HashMap’s initial capacity)
  *        nor you have to rehash when is getting full.
  *
+ * Implementations in other languages:
+ * Java: https://docs.oracle.com/en/java/javase/15/docs/api/java.base/java/util/TreeMap.html
+ * C++: https://en.cppreference.com/w/cpp/container/map
+ * Python: none
+ *
  */
 class TreeMap {
   // tag::constructor[]
@@ -92,6 +97,16 @@ class TreeMap {
   }
   // end::delete[]
 
+  lastEntry() {
+    const node = this.tree.getRightmost();
+    return node ? [node.value, node.data()] : [];
+  }
+
+  firstEntry() {
+    const node = this.tree.getLeftmost();
+    return node ? [node.value, node.data()] : [];
+  }
+
   // tag::iterators[]
   /**
    * Default iterator for this map

src/data-structures/maps/tree-maps/tree-map.spec.js

@@ -0,0 +1,43 @@
+// some parts tested on src/data-structures/maps/map.spec.js
+
+const TreeMap = require('./tree-map');
+
+describe('TreeMap: keep values sorted', () => {
+  let map;
+
+  beforeEach(() => {
+    map = new TreeMap();
+  });
+
+  describe('when map is empty', () => {
+    describe('.lastEntry and .firstEntry', () => {
+      it('should get last/first entry', () => {
+        expect(map.lastEntry()).toEqual([]);
+        expect(map.firstEntry()).toEqual([]);
+      });
+    });
+  });
+
+  describe('when map has entries', () => {
+    beforeEach(() => {
+      map.set(20, { title: '3sum', passed: true });
+      map.set(30, { title: '3sum', passed: false });
+      map.set(10, { title: '2sum', passed: true });
+      map.set(5, { title: '4sum', passed: false });
+    });
+
+    describe('.lastEntry and .firstEntry', () => {
+      it('should get last/first entry', () => {
+        expect(map.lastEntry()).toEqual([
+          30,
+          { title: '3sum', passed: false },
+        ]);
+
+        expect(map.firstEntry()).toEqual([
+          5,
+          { title: '4sum', passed: false },
+        ]);
+      });
+    });
+  });
+});