Question

我正在尝试为学校作业创建自己的哈希类，但在获得部分路径之后，我遇到了一个我无法调试的错误。

当我运行我的项目时，我得到一个“Debug Assertion Failed！... Expression：invalid null pointer”。

程序在我的驱动程序文件（test.cpp）的第16行给出了此错误。在我看来，指向我班级的指针不是NULL。

任何有关导致此错误的原因以及我如何解决此问题的任何帮助都将非常感激。

//Hash.h

#include <string>
struct Student
{
    std::string name;
    std::string id;
};

class MyHash{
public:
    MyHash();
    int hashCode(int, int);
    void insertItemCollision(std::string, std::string);
    Student retrieveItem(std::string);
    Student students[100];
};

//Hash.cpp
#include <iostream>
#include "Hash.h"


MyHash::MyHash()
{
    for(int i = 0; i < 100; i++)
    {
        students[i].id.assign(NULL);    
        students[i].name.assign(NULL);
    }
}



int MyHash::hashCode(int id, int max)
{

  return (id % max);
}

void MyHash::insertItemCollision(std::string id, std::string name)
{
    int idInt = atoi(id.c_str());
    int location;


  location = hashCode(idInt, 100);
  while (students[location].id != "")
    location = (location + 1) % 100;
  students[location].id = id;
  students[location].name = name;
}


Student MyHash::retrieveItem(std::string id)
{
  int location;
  int startLoc;
  int idInt = atoi(id.c_str());
  bool moreToSearch = true;
  bool found;
  Student item;

  startLoc = hashCode(idInt, 100);
  location = startLoc;
  do
  {
      if (students[location].id == id || students[location].id == "")
      moreToSearch = false;
    else
      location = (location + 1) % 100;
  } while (location != startLoc && moreToSearch);
  found = (students[location].id == id);
  if (found)
    item = students[location];
  return item;
}


//test.cpp
#include <iostream>
#include<string>
#include<fstream>
#include "Hash.h"
using namespace std;


int read(string[]);
void splitString(string, Student&);
void init(string[], Student[], int);

int main()
{
    int size;
    string input[100];
    MyHash* h = new MyHash();
    size = read(input); 
    init(input, h->students, size);

    system("pause");
    return 0;
}

int read(string st[])
{
    int size = 0;
    ifstream infilestream;
    infilestream.open("test.txt");


    for(int i = 0; infilestream.good(); i++)
    {
        getline(infilestream, st[i]);
        cout<<st[i] <<endl;
        size++;
    }
    infilestream.close();
    return size;
}

void splitString(string record, Student& s)
{
    s.id = record.substr(0, 4);
    s.name = record.substr(5, record.length());
}

void init(string inputs[], Student stus[], int size)
{
    for(int i = 0;i < size; i++)
    {
        splitString(inputs[i],stus[i]);
        cout << stus[i].name << " " << stus[i].id << endl;
    }
}

//test.txt
9892 Zack Lewis
4592 Ken Rodriguez
9819 Anderson Clark
1519 Ben Robinson
4597 Abigail Martinez
8542 Madison Garcia
6113 Mia Thompson
8591 Chloe Martin
9491 Daniel Harris
1698 Aiden White
5984 Alexander Walker
6541 Ethan Jackson
9549 Michael Thomas
5949 Emily Anderson
9861 Ava Taylor
5412 Noah Moore
6262 Olivia Wilson
1954 Jayden Miller
4954 William Davis
9567 Emma Brown
5195 Mason Jones
9195 Isabella Williams
5199 Sophia Johnson
1294 Jacob Smith

Answer 1

此

MyHash::MyHash()
{
    for(int i = 0; i < 100; i++)
    {
        students[i].id.assign(NULL);    
        students[i].name.assign(NULL);
    }
}

不正确。这是正确的

MyHash::MyHash()
{
}

您不必向std::string“指定NULL”。 std::string 的默认构造函数自动创建一个空字符串。事实上，为std :: string分配NULL是一个错误，因为这个方法总是需要一个指向C字符串的指针。

实际上，您根本不需要MyHash构造函数，因为默认构造函数会执行您在编写的版本中尝试执行的所有操作。你看C ++比你想象的要容易。

调试断言失败

1 个答案: