手写最大堆-实现

 1 class Heap {
 2     public:
 3     void push(int x){
 4         heap.push_back(x);
 5         size += 1;
 6         int now = size;
 7         while(now!=1) {
 8             int parent = now / 2;
 9             if(heap[now] > heap[parent])
10                 swap(heap[now], heap[parent]);
11             else break;
12             now = parent;
13         }
14     }
15     
16     bool empty(){
17         return size == 0;
18     }
19     
20     int top(){
21        return heap[1];
22     }
23     
24     int _size(){
25         return size;
26     }
27     
28     int pop(){
29         int ans = heap[1];
30         swap(heap[size], heap[1]);
31         heap.pop_back();
32         size -= 1;
33         int now = 1;
34         while(now * 2 <= size){
35             int child = now * 2;
36             if(child + 1 <=size && heap[child+1] > heap[child])
37                 child += 1;
38             if(heap[now] < heap[child])
39                 swap(heap[now], heap[child]);
40             else break;
41             now = child;
42         }
43         return ans;
44     }
45     
46     private:
47     vector<int> heap = {0};
48     int size = 0;
49 };
50 
51 
52 class Solution {
53 public:
54     vector<int> GetLeastNumbers_Solution(vector<int> input, int k) {
55         Heap h;
56         vector<int> ans;
57         if(k>input.size()) return ans;
58         for(auto it: input) {
59             if(h._size()<k)
60                 h.push(it);
61             else{
62                 if(h.top()>it) {
63                     h.pop();
64                     h.push(it);
65                 }
66             }
67         }
68         while(!h.empty()) ans.push_back(h.pop());
69         reverse(ans.begin(), ans.end());
70         return ans;
71     }
72 };