public void Push(HeapNodeWord node)
{
if (++tail >= arr.Length)
{
throw new Exception("Heap is full");
}
arr[tail] = node;
int currentIndex = tail;
int parentIndex = GetParentIndex(currentIndex);
while (parentIndex >= 0 && FirstIsGreater(arr[parentIndex], arr[currentIndex]))
{
arr[currentIndex] = arr[parentIndex];
arr[parentIndex] = node;
currentIndex = parentIndex;
parentIndex = GetParentIndex(currentIndex);
}
}
public IList <string> TopKFrequent(string[] words, int k)
{
var dict = new Dictionary <string, int>();
foreach (var word in words)
{
dict[word] = dict.ContainsKey(word) ? dict[word] + 1 : 1;
}
var heap = new MinHeap(k + 1);
foreach (var key in dict.Keys)
{
var node = new HeapNodeWord();
node.count = dict[key];
node.word = key;
heap.Push(node);
if (heap.Count > k)
{
heap.Pop();
}
}
var res = new List <string>();
while (heap.Count > 0)
{
var node = heap.Pop();
res.Insert(0, node.word);
//res.Add(node.word);
}
return(res);
}
public MinHeap(int size)
{
arr = new HeapNodeWord[size];
}
private bool FirstIsGreater(HeapNodeWord node1, HeapNodeWord node2)
{
return((node1.count == node2.count) ?
String.Compare(node1.word, node2.word) == -1 // -1 aaa < zzz
: node1.count > node2.count);
}
