C++ bad_alloc 在 vector <int> intList 上使用 vecList.pop_back()

Question

全部，完成学期并使用 vector 完成此学生作业。在执行 int remove() 函数期间出现间歇性 bad_alloc 错误和核心转储。我相信当我使用 intList.pop_back() 时会发生这种情况。这是我第一次用 vector 列表做任何事情，我很想知道为什么会这样，以及如何正确地做这件事以避免将来出现这个问题。任何想法将不胜感激。

#include <iostream>
#include <cstdlib>
#include <ctime>

using std::cout; 
using std::endl; 
using std::vector;

int remove(vector<int> *intList, int noOfElements, int removeItem);
void printResult(int removeItem, int removeReturn, int listLength);

int main()
{
    // variable declarations
    int removeReturn = 0;
    int removeItem = 0;
    unsigned int listLength = 0;
    unsigned int counter = 0;
    time_t seconds;
    vector<int> intList;

    // getting the time in seconds as a seed
    time(&seconds);
    // seeding the random number generator
    srand((unsigned int) seconds);
    // getting the random length for the calculations
    listLength = rand() % (100 - 1 + 1) + 1;
    std::cout << std::endl << "listLength is: " << listLength << std::endl;
    // populate the array with numbers from 1 to listLength
    std::cout << "Array:" << std::endl;
    for(counter = 0; counter < listLength; counter++)
    {
        intList.push_back(rand() % (listLength - 1 + 1) + 1);
        std::cout << intList.back() << " ";
        if(counter > 0 && (counter + 1) % 10 == 0)
            std::cout << std::endl;
    }
    std::cout << std::endl;
    listLength = intList.size();
    // generate a number in range to use for the search
    removeItem = rand() % (listLength - 1 + 1) + 1;
    // search for the number and delete it if found
    // changing the size of the vector array as you do
    std:: cout << "Searching for " << removeItem << " for removal." << std::endl;
    removeReturn = remove(&intList, listLength, removeItem);
    listLength = intList.size();
    // output the results of the operation
    printResult(removeItem, removeReturn, listLength);

    return 0;
} // end main

int remove(std::vector<int> *intList, int noOfElements, int removeItem)
{
    int counter;
    int icounter;

    // check to see if the vector list is empty
    // if it is, exit with -1 (error message)
    if(intList->empty())
        return -1;
    // assuming there is data in the vector list,
    // loop through and look for the element
    for(counter = 0; counter < noOfElements; counter++)
    {
        // if we do find an occurrence of the data in the vector list
        if(intList->at(counter) == removeItem)
        {
            // overwrite it with the next piece of data
            // and move the rest of the data up by one element
            for(icounter = counter; icounter < noOfElements - 1; icounter++)
            {
                    intList[icounter] = intList[icounter + 1];
            }
            // now that we have moved every data piece up one element
            // delete the last element from the list
            intList->pop_back();
            // return the position where the data was found
            return counter;
        }
    }
    // return 0 because we didn't find the data
    return 0;
} // end remove

void printResult(int removeItem, int removeReturn, int listLength)
{
    if(removeReturn > 0)
    {
        std::cout << "Found " << removeItem << " at position " << removeReturn +  << std::endl;
        std::cout << "and deleted it from the list " << std::endl;
        std::cout << "The new list length is " << listLength << std::endl;
    }
    else if(removeReturn == -1)
        std::cout << "The list was empty" << std::endl;
    else if(removeReturn == 0)
    {
        std::cout << "Value " << removeItem << " not found" << std::endl;
        exit(101);
    }
} // end printResult

Answer 1

如果您正在尝试做的是在 std::vector 中搜索一个项目并将其删除，那么这样做不需要复杂的函数:

#include <algorithm>
//...
intList.erase(std::remove(intList.begin(), intList.end(), removeItem), intList.end());

这一行完成了整个 remove 函数试图做的所有事情。

http://www.cplusplus.com/reference/algorithm/remove/ http://www.cplusplus.com/reference/vector/vector/erase/

一般来说，学习使用STL算法。在容器中移动、删除和排序项目是在程序中例行完成的操作，因此存在执行这些任务的算法。