我的插入功能已经正确处理了碰撞,但我希望能够计算每种不同散列方式(链接,线性探测和二次探测)中的碰撞次数。我该怎么做呢?
到目前为止我的代码:
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <iterator>
#include <ctime>
#include "Chaining.h"
#include "QuadraticProbing.h"
#include "LinearProbing.h"
using namespace std;
int main()
{
int collision_count = 0;
float diff = 0.0;
clock_t tStart, tStop;
string ITEM_NOT_FOUND = "ITEM_NOT_FOUND";
std::vector<std::string> DataArray;
std::copy(std::istream_iterator<std::string>(std::ifstream("OHenry.txt")),istream_iterator<string>(),back_inserter(DataArray));
std::vector<std::string> QueryArray;
std::copy(std::istream_iterator<std::string>(std::ifstream("queries.txt")),istream_iterator<string>(),back_inserter(QueryArray));
cout << "Testing chaining probing...\n";
HashTable_chaining ChainingHT( ITEM_NOT_FOUND, 101 );
int i = 0;
double average_c = 0.0;
double total_c = 0.0;
double temp_c = 0.0;
while(i != DataArray.size())
{
tStart = clock();
ChainingHT.insert(DataArray[i]);
tStop = clock();
total_c = tStop - tStart;
temp_c = total_c + temp_c;
average_c = total_c / DataArray.size();
if(DataArray[i] != DataArray[NULL])
{
collision_count++;
}
i++;
}
cout<<"The number of collisions using Chaining is: "<<collision_count<<endl;
cout<<"The average time per insertion using Chaining is: "<<average_c<<endl;
system("pause");
// Quadratic Probing
cout << "Testing quadratic probing...\n";
HashTable_chaining QuadraticProbingHT( ITEM_NOT_FOUND, 101 );
int j = 0;
int collision_count_quadratic = 0;
double average_qp = 0;
while(j != DataArray.size())
{
clock_t tStartq = clock();
QuadraticProbingHT.insert(DataArray[j]);
if(DataArray[j] != DataArray[NULL])
{
collision_count_quadratic++;
}
j++;
average_qp = (((double)(clock() - tStartq)/CLOCKS_PER_SEC) + average_qp) / DataArray.size();
}
cout<<"The number of collisions using Quadratic is: "<<collision_count<<endl;
cout<<"The average time per insertion using Quadratic is: "<<average_qp<<endl;
答案 0 :(得分:6)
哈希表本身可以报告它所看到的分离数量,而不会暴露其内部实现。
对于使用探测(任何类型)的哈希表,colissions的数量等于位于与其哈希码不一致的索引处的元素的数量(这是因为它们通常已存储的位置已经是被占据)。
对于使用链接的哈希表,colissions的数量等于哈希表中的项目数减去占用的桶数(换句话说,计算除每个桶中第一个之外的所有插入项)。这也很直观。
所以我要做的就是给每个散列表一个count_colissions()
方法,用相应的方法计算O(n)时间内的colissions数量并返回它。