Fortune left France Basic Class 5_1 structure design RandomPool

Problem:
　　Design RandomPool structure
　　[Title] design a structure has the following three functions in the structure:
　　　　INSERT (key): the addition of a key to the structure, do not repeat added.
　　　　delete (key): remove the original structure of a key.
　　　　getRandom (): returns the probability of any other key structures.

　　[Required] Insert, delete and getRandom time complexity methods are O (1)

Solution:
　　Use two hash table is a record label, a record keyword
　　here is a key point is that the probability of return such as a keyword
　　if using a simple hash table for storage, then there is a problem when deleting data , the hash table will be generated such that the intermediate blank data
　　is preferably generated null data to avoid the intermediate approach is to delete the data to be exchanged with the data in the table at the end
　　and then remove the last data directly, it is necessary to use two hash tables

 

Code:　　

  1 #pragma once
  2 #include <iostream>
  3 #include <hash_map>
  4 #include <string>
  5 #include <time.h>
  6 #include <stdlib.h>
  7 
  8 using namespace std;
  9 
 10 template<class T>
 11 class RandomPool
 12 {
 13 public:
 14     void insert(T key);
 15     void del(T key);
 16     T getRandom();
 17     void getPrint(T key);
 18     void getPrint(int index);
 19 
 20 private:
 21     hash_map<T, int>KeyMap;
 22     hash_map<int, T>IndexMap;
 23     int size = 0;
 24 };
 25 
 26 
 27 template<class T>
 28 void RandomPool<T>::insert(T key)
 29 {
 30     if (KeyMap.find(key) == KeyMap.end())
 31     {
 32         KeyMap[key] = this->size;
 33         IndexMap[this->size] = key;
 34         ++(this->size);
 35         cout << "add succeed!" << endl;
 36     }
 37     else
 38         cout << "add filed!" << endl;
 39 }
 40 
 41 
 42 template<class T>
 43 void RandomPool<T>::del(T key)
44 is  {
 45      Auto PTR = KeyMap.find (Key);
 46 is      IF (PTR == KeyMap.end ())
 47      {
 48          COUT << " !! Filed there IS Not Delete Key ExSite The " << endl;
 49          return ;
 50      }
 51      // switching elements to find the last element 
52 is      T IndexMap TEMP = [- ( the this -> size)]; // keyword last element, while the elements of the hash table is deleted 
53 is      int index KEYMAP = [Key]; // to delete the position of the element 
54 is      KEYMAP [TEMP] = index;
55      IndexMap [index] = TEMP; // the last element To delete a position of the element
 56      // actually deleted 
57 is      KeyMap.erase (PTR);
 58      IndexMap.erase (IndexMap.find (index));
 59  }
 60  
61 is Template < class T>
 62 is T RandomPool <T> :: getRandom ()
 63 is  {
 64      IF ( the this -> size == 0 )
 65      {
 66          COUT << " The Map IS empty! " << endl;
 67      }
 68      the else
69      {
 70          int index = ( int ) ((RAND ()% ( 99 + . 1 ) / ( Double ) ( 99 + . 1 )) * ( the this -> size)); // generate a random position 
71 is          return IndexMap [index ];
 72      }
 73 is  }
 74  
75 Template < class T>
 76  void RandomPool <T> :: getPrint (T Key)
 77  {
 78      IF (KeyMap.find (Key) == KeyMap.end ())
 79          COUT <<"the key is not exsite!" << endl;
 80     else
 81         cout << KeyMap[key] << endl;
 82 }
 83 
 84 template<class T>
 85 void RandomPool<T>::getPrint(int index) 
 86 {
 87     if (IndexMap.find(index) == IndexMap.end())
 88         cout << "the key is not exsite!" << endl;
 89     else
 90         cout << IndexMap[index] << endl;
 91 }
 92 
 93 
 94 void Test()
 95 {
 96     srand((unsigned)time(NULL));
 97     RandomPool<string>map;
 98     map.insert("zz");
 99     map.insert("zw");
100     map.insert("ww");
101     map.insert("wz");
102 
103     cout << map.getRandom() << endl;
104     map.getPrint(2);
105     map.getPrint("ww");
106     map.del("zw");
107     map.getPrint("zw");
108 }