Question

我在使用这个程序时遇到了一些问题，我知道我可以使用矢量，但我只是尝试使用数组。一旦程序达到初始数组大小1000，它应该在复制数据后将数组加倍（在本例中为2000）。因此，例如，如果我有一个包含3000个名称的列表，它会在1000处加倍，然后再在2000处加倍 - 使总列表4000.我不完全确定为什么在我将数组大小加倍后它会崩溃。有人可以帮我这个吗？

#include <iostream>
#include <fstream>
#include <string.h>
using namespace std;

struct Information {
  char functionality;
  string SSN;
  string name;
};

Information* person;
int numPeople = 1000;
int numRetrieved = 0;
int numArray = 0;
int numInserted = 0;
int numDeleted = 0;


void doubleArray(Information *person){
  numPeople = numPeople * 2;
  Information* temp = new Information[numPeople];
  memcpy(temp, person, numPeople/2);
  delete[] person;
  person = temp;
  cout << "Person 1: " << person[0].name << " " << person[0].SSN << endl;
}
//Currently not using this until I figure out the double...
void halfArray(Information *person){
  numPeople = numPeople / 2;
}

void deleteInfo(Information *person, string SSN){
  for(int i = 0; i < numArray; i++){
    if(person[i].SSN == SSN){
      for(int k = i; k < numArray-1; k++){
        person[k].SSN = person[k+1].SSN;
        person[k].name = person[k+1].name;
      } 
      numArray--;
      numDeleted++;

      if((numArray+1) < (numPeople / 4)){
        //halfArray(person);
      }
    }
  }
}

void retrieve(Information *person, string findSSN, int lastPerson){
  for(int i = 0; i < lastPerson; i++){
    if(person[i].SSN == findSSN){
        numRetrieved++;
    }
  }
}

void insert(Information *person, string SSN, string name){
  if(numArray == (numPeople - 1)){
    doubleArray(person);
  }

  bool dontInsert = false;
  for(int i = 0; i <= numArray; i++){
    if(person[i].SSN == SSN){
      dontInsert = true;    
    }
  }

  if(dontInsert){
    dontInsert = false;
  }else{
    person[numArray].SSN = SSN;
    person[numArray].name = name;
    numArray++;
    numInserted++;
  }
}

int main(int argc, char* argv[]) {
    person = new Information[numPeople];
    char firstLetter;
    string SSN, firstName, lastName, name; 
    fstream input(argv[1]);

    for(int i = 0; !input.eof(); i++){
        input >> firstLetter >> SSN >> firstName >> lastName;
        name = firstName + " " + lastName;

        switch(firstLetter){
            case 'd':{
                deleteInfo(person, SSN);
                break;
            }
            case 'i':{
                insert(person, SSN, name);
                break;
            }
            case 'r':{
                retrieve(person, SSN, numArray);
                break;
            }
        }
    }
    input.close();
}

Answer 1

您删除了Information*所指向的内存，但是您拥有该指针的副本，并将其分配给temp变量在doubleArray之外无效。

让我们说传入的人的价值是0xC001C001;

void doubleArray(Information *person){
  numPeople = numPeople * 2;
  Information* temp = new Information[numPeople];
  memcpy(temp, person, numPeople/2);
  delete[] person;
  person = temp;
  cout << "Person 1: " << person[0].name << " " << person[0].SSN << endl;
}

您创建一个新的指针temp，其值为0xBAD1BAD1。删除人（0xC001C001），然后将0xBAD1BAD1分配给person。然后在插入函数中继续执行...

void insert(Information *person, string SSN, string name){
  if(numArray == (numPeople - 1)){
    doubleArray(person);
  }

  bool dontInsert = false;
  for(int i = 0; i <= numArray; i++){
    if(person[i].SSN == SSN){
      dontInsert = true;    
    }
  }

此处的person变量仍具有已取消分配的值0xC001C001。当您使用person[i].SSN推荐人时，您的计划会爆炸。

当您想要更改指针时，经典模式是传递指针指针。（两星级节目）

void redo(P** p)
{
  P* temp = new P();
  delete *p;
  *p = temp;
}

复制数组 - 加倍数组后崩溃

1 个答案: