我目前正在嘗試編寫一個程序,該程序創建一個哈希表,使用向量的矢量作爲我的衝突解決方法。使用矢量矢量創建哈希表?
我面臨的問題是,在運行時,向量的矢量被創建,但所有的入口向量仍然大小爲0.我知道我的put函數有問題,但我不知道在哪裏/爲什麼。
這是我第一次創建一個哈希表,我會很感激任何問題的幫助。我的目標是創建一個入口向量的向量,並且每個入口都有其關聯的鍵和值。在找到新的Entry鍵的散列值後,它應該檢查Entry矢量的鍵值以查看鍵是否已經存在。如果是,則更新該密鑰的值。
這是table.cpp的一個片段:
Table::Table(unsigned int maximumEntries) : maxEntries(100){
this->maxEntries = maximumEntries;
this->Tsize = 2*maxEntries;
}
Table::Table(unsigned int entries, std::istream& input){ //do not input more than the specified number of entries.
this->maxEntries = entries;
this->Tsize = 2*maxEntries;
std::string line = "";
int numEntries = 0;
getline(input, line);
while(numEntries<maxEntries || input.eof()){ // reads to entries or end of file
int key;
std::string strData = "";
convertToValues(key, strData, line);
put(key, strData); // adds each of the values to the tab;e
numEntries++;
getline(input,line);
}
}
void Table::put(unsigned int key, std::string data){
Entry newEntryObj(key,data); //create a new Entry obj
put(newEntryObj);
}
void Table::put(Entry e){ // creating the hash table
assert(currNumEntries < maxEntries);
int hash = (e.get_key() % Tsize);
Entry newEntry = Entry(e.get_key(), e.get_data());
for(int i = 0; i < hashtable[hash].size(); i++){
if (e.get_key() == hashtable[hash][i].get_key()){
hashtable[hash][i].set_data(e.get_data());
}
else{
hashtable[hash].push_back(newEntry); // IF KEY DOESNT EXIST, ADD TO THE VECTOR
}
}
}
這是Table.h
#ifndef table_h
#define table_h
#include "entry.h"
#include <string>
#include <istream>
#include <fstream>
#include <iostream>
#include <vector>
class Table{
public:
Table(unsigned int max_entries = 100); //Builds empty table with maxEntry value
Table(unsigned int entries, std::istream& input); //Builds table designed to hold number of entires
void put(unsigned int key, std::string data); //creates a new Entry to put in
void put(Entry e); //puts COPY of entry into the table
std::string get(unsigned int key) const; //returns string associated w/ param, "" if no entry exists
bool remove(unsigned int key); //removes Entry containing the given key
friend std::ostream& operator<< (std::ostream& out, const Table& t); //overloads << operator to PRINT the table.
int getSize();
std::vector<std::vector<Entry>> getHashtable();
private:
std::vector<std::vector<Entry>> hashtable; //vector of vectors
int Tsize; //size of table equal to twice the max number of entries
int maxEntries;
int currNumEntries;
#endif /* table_h */
};
和Entry.h:
#include <string>
#include <iosfwd>
class Entry {
public:
// constructor
Entry(unsigned int key = 0, std::string data = "");
// access and mutator functions
unsigned int get_key() const;
std::string get_data() const;
static unsigned int access_count();
void set_key(unsigned int k);
void set_data(std::string d);
// operator conversion function simplifies comparisons
operator unsigned int() const;
// input and output friends
friend std::istream& operator>>
(std::istream& inp, Entry &e);
friend std::ostream& operator<<
(std::ostream& out, Entry &e);
private:
unsigned int key;
std::string data;
static unsigned int accesses;
};
只是一個側面的問題:爲什麼不使用'std :: unordered_map'? – nakiya
我不允許使用