Aeron - Rock

lib/heapsort.js

@@ -1,8 +1,14 @@
+import MinHeap from "./minheap";
+
 // This method uses a heap to sort an array.
 // Time Complexity:  ?
 // Space Complexity: ?
 function heapsort(list) {
-  throw new Error('Method not implemented yet...');
+  let heap = new MinHeap;
+
+  while(!heap.isEmpty()) {
+    list.push(heap.remove());
+  }  
 };
 
 module.exports = heapsort;

lib/minheap.js

@@ -9,20 +9,31 @@ class MinHeap {
   constructor() {
     this.store = [];
   }
-
   // This method adds a HeapNode instance to the heap
-  // Time Complexity: ?
-  // Space Complexity: ?
+  // Time Complexity: generally Log N
+  // Space Complexity: equal to the nodes in the heap - 1
+
   add(key, value = key) {
-    throw new Error("Method not implemented yet...");
+
+    const node = new HeapNode(key, value);
+    this.store.push(node);
+    if (this.store.length > 1) {
+      this.heapUp(this.store.length - 1);
+    }
   }
 
   // This method removes and returns an element from the heap
   //   maintaining the heap structure
   // Time Complexity: ?
   // Space Complexity: ?
   remove() {
-    throw new Error("Method not implemented yet...");
+    if (!this.store.length) return;
+
+    this.swap(0, this.store.length - 1);
+    const removed = this.store.pop();
+    this.heapDown(0);
+
+    return removed.value;
   }
 
 
@@ -41,7 +52,7 @@ class MinHeap {
   // Time complexity: ?
   // Space complexity: ?
   isEmpty() {
-    throw new Error("Method not implemented yet...");
+    return !this.store
   }
 
   // This helper method takes an index and
@@ -50,23 +61,47 @@ class MinHeap {
   // Time complexity: ?
   // Space complexity: ?
   heapUp(index) {
-    throw new Error("Method not implemented yet...");
+
+    const parentIndex = Math.floor((index - 1) / 2);
+    const parentNode = this.store[parentIndex];
+    const newNode = this.store[index];
+
+    if (newNode.key < parentNode.key) {
+      this.swap(index, parentIndex);
+      if (parentIndex > 0) {
+        this.heapUp(parentIndex)
+      }
+    }
   }
 
   // This helper method takes an index and 
   //  moves it up the heap if it's smaller
   //  than it's parent node.
   heapDown(index) {
-    throw new Error("Method not implemented yet...");
+    const left = 2 * index + 1
+    const right = 2 * index + 2
+    let smallest = index;
+
+    if((left < this.store.length) && (this.store[left].key < this.store[smallest].key)) {
+      smallest = left;
+    }
+
+    if ((right < this.store.length) && (this.store[right].key < this.store[smallest].key)) {
+      smallest = right;
+    }
+
+    if (index !== smallest){
+      this.swap(index, smallest);
+      this.heapDown(smallest);
+    }
   }
 
+
   // If you want a swap method... you're welcome
   swap(index1, index2) {
     const s = this.store;
     [s[index1], s[index2]] = [s[index2], s[index1]];
   }
 }
 
-module.exports = {
-  MinHeap
-};
+module.exports = { MinHeap };