《数据结构与算法分析：C语言描述》复习——第五章“堆”——二叉堆

  1 // My implementation for priority queue using binary heap.
  2 #include <iostream>
  3 #include <string>
  4 #include <vector>
  5 using namespace std;
  6 
  7 template <class T>
  8 class PriorityQueue {
  9 public:
 10     PriorityQueue() {
 11         m_data.push_back(0);
 12     }
 13     
 14     PriorityQueue(const vector<T> &data) {
 15         m_data.push_back(0);
 16         for (size_t i = 0; i < data.size(); ++i) {
 17             m_data.push_back(data[i]);
 18         }
 19         _makeHeap();
 20     }
 21     
 22     bool empty() {
 23         return m_data.size() == 1;
 24     }
 25     
 26     size_t size() {
 27         return m_data.size() - 1;
 28     }
 29     
 30     T top() {
 31         return m_data[1];
 32     }
 33     
 34     void push(const T &val) {
 35         m_data.push_back(val);
 36         
 37         int n = size();
 38         int i = n;
 39         
 40         while (i > 1) {
 41             if (m_data[i / 2] < m_data[i]) {
 42                 _swap(m_data[i / 2], m_data[i]);
 43                 i /= 2;
 44             } else {
 45                 break;
 46             }
 47         }
 48     }
 49     
 50     void pop() {
 51         int n = size();
 52         m_data[1] = m_data[n];
 53         m_data.pop_back();
 54         --n;
 55         
 56         int i = 1;
 57         T max_val;
 58         while (i * 2 <= n) {
 59             max_val = i * 2 == n ? m_data[i * 2] : _max(m_data[i * 2], m_data[i * 2 + 1]);
 60             if (m_data[i] < max_val) {
 61                 if (max_val == m_data[i * 2] || i * 2 == n) {
 62                     _swap(m_data[i], m_data[i * 2]);
 63                     i = i * 2;
 64                 } else {
 65                     _swap(m_data[i], m_data[i * 2 + 1]);
 66                     i = i * 2 + 1;
 67                 }
 68             } else {
 69                 break;
 70             }
 71         }
 72     }
 73     
 74     void clear() {
 75         m_data.resize(1);
 76     }
 77 
 78     ~PriorityQueue() {
 79         m_data.clear();
 80     }
 81 private:
 82     vector<T> m_data;
 83     
 84     T _max(const T &x, const T &y) {
 85         return x > y ? x : y;
 86     }
 87     
 88     void _swap(T &x, T &y) {
 89         T tmp;
 90         
 91         tmp = x;
 92         x = y;
 93         y = tmp;
 94     }
 95     
 96     void _makeHeap() {
 97         int n = size();
 98         int i, j;
 99         T max_val;
100         
101         for (j = n / 2; j >= 1; --j) {
102             i = j;
103             while (i * 2 <= n) {
104                 max_val = i * 2 == n ? m_data[i * 2] : _max(m_data[i * 2], m_data[i * 2 + 1]);
105                 if (m_data[i] < max_val) {
106                     if (max_val == m_data[i * 2] || i * 2 == n) {
107                         _swap(m_data[i], m_data[i * 2]);
108                         i = i * 2;
109                     } else {
110                         _swap(m_data[i], m_data[i * 2 + 1]);
111                         i = i * 2 + 1;
112                     }
113                 } else {
114                     break;
115                 }
116             }
117         }
118 
119         n = size();
120         cout << ‘[‘;
121         for (int i = 1; i <= n; ++i) {
122             cout << m_data[i] << ‘ ‘;
123         }
124         cout << ‘]‘ << endl;
125     }
126 };
127 
128 int main()
129 {
130     vector<int> v;
131     v.push_back(1);
132     v.push_back(2);
133     v.push_back(3);
134     v.push_back(4);
135     v.push_back(5);
136     v.push_back(6);
137     v.push_back(7);
138     v.push_back(8);
139     PriorityQueue<int> pq(v);
140     string s;
141     int n;
142     
143     while (cin >> s) {
144         if (s == "push") {
145             cin >> n;
146             pq.push(n);
147         } else if (s == "pop") {
148             pq.pop();
149         } else if (s == "top") {
150             cout << pq.top() << endl;
151         } else if (s == "end") {
152             while (!pq.empty()) {
153                 pq.pop();
154             }
155             break;
156         }
157     }
158     
159     return 0;
160 }