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This commit is contained in:
Slava Kim
2014-02-24 20:22:24 -08:00
parent a6410c4af7
commit 97f7ccfa63
1 changed files with 17 additions and 10 deletions
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27
packages/binary-heap/max-heap.js
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@@ -4,7 +4,7 @@
// Object:
// - id - String - unique id of the item
// - value - Any - the data value
// the contents of initData is retained
// each value is retained
MaxHeap = function (comparator, initData) {
if (! _.isFunction(comparator))
throw new Error('Passed comparator is invalid, should be a comparison function');
@@ -24,12 +24,12 @@ MaxHeap = function (comparator, initData) {
// The Heap data-structure implemented as a 0-based contiguous array where
// every item on index idx is a node in a complete binary tree. Every node can
// have leaves on indexes idx*2+1 and idx*2+2, except for the lists. Every
// have children on indexes idx*2+1 and idx*2+2, except for the leaves. Every
// node has a parent on index (idx-1)/2;
self._heap = [];
// If the initial array is passed, we can build the heap in linear time
// complexity (O(N)) compared to linearithmetic time complexity (O(nlogn)) if
// complexity (O(N)) compared to linearithmic time complexity (O(nlogn)) if
// we push elements one by one.
if (_.isArray(initData))
self._initFromData(initData);
@@ -41,7 +41,7 @@ _.extend(MaxHeap.prototype, {
var self = this;
self._heap = _.map(data, function (o) {
return { id: EJSON.clone(o.id), value: o.value };
return { id: o.id, value: o.value };
});
_.each(data, function (o, i) {
@@ -64,11 +64,11 @@ _.extend(MaxHeap.prototype, {
var right = rightChildIdx(idx);
var largest = idx;
if (left < self.size() && self._maxIndex(largest, left) === left) {
largest = left;
if (left < self.size()) {
largest = self._maxIndex(largest, left);
}
if (right < self.size() && self._maxIndex(largest, right) === right) {
largest = right;
if (right < self.size()) {
largest = self._maxIndex(largest, right);
}
if (largest === idx)
@@ -133,7 +133,11 @@ _.extend(MaxHeap.prototype, {
var idx = self._heapIdx.get(id);
self._heap[idx].value = value;
// Fix the new value's position
// Either bubble new value up if it is greater than its parent
self._upHeap(idx);
// or bubble it down if it is smaller than one of its children
self._downHeap(idx);
} else {
self._heapIdx.set(id, self._heap.length);
@@ -152,8 +156,10 @@ _.extend(MaxHeap.prototype, {
self._swap(idx, last);
self._heap.pop();
self._heapIdx.remove(id);
self._downHeap(idx);
// Fix the swapped value's position
self._upHeap(idx);
self._downHeap(idx);
} else {
self._heap.pop();
self._heapIdx.remove(id);
@@ -173,6 +179,7 @@ _.extend(MaxHeap.prototype, {
self._heap = [];
self._heapIdx.clear();
},
// iterate over values in no particular order
forEach: function (iterator) {
var self = this;
_.each(self._heap, function (obj) {
@@ -206,7 +213,7 @@ _.extend(MaxHeap.prototype, {
for (var i = 1; i < self._heap.length; i++)
if (self._maxIndex(parentIdx(i), i) !== parentIdx(i))
throw new Error("An item with id " + self._heap[i].id +
" has a parent younger than him: " +
" has a parent younger than it: " +
self._heap[parentIdx(i)].id);
}
});