我知道导致段错的原因,但为什么呢？

Question

好的,所以我有一个简单的c ++程序,应该在由int组成的数组上运行几个排序算法并跟踪每个人所需的时间..非常基本,但是我遇到了问题.

当程序首次启动时,它会询问您在阵列中需要多少项.我的任务涉及将数组设置为从100个项目到750000的特定长度.它将处理许多值,包括高达600000左右.当我尝试750000时,它会立即发生段错误.这里和那里的几个小姐让我发现当初始化第四个数组(所有相同长度)时会发生错误.奇怪的是它只发生在我的操作系统上; 在我的学校,它没有问题.(我在最新的ubuntu,而我的学校使用redhat.不确定这是否有用)

我将包含完整的代码仅供参考,但段错误发生在第27行:

int array1[num], array2[num], array3[num], array4[num]; // initialize arrays 

我知道这是因为我在不同的行上初始化每个数组,并在其间放置couts.array1,2和3被初始化,然后是segfaults.同样,这仅在阵列长于约600000左右时发生.任何不太好的工作.

完整代码:

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

using namespace std;

void insertionSort(int array[], int size);
void bubbleSort(int array[], int size);
void mergeSort(int array[], int first, int last, int size);
void quickSort(int array[], int size);

int main()
{

    cout << endl << endl << "\t\t**** Extra Credit Assignment- Sorting ****" << endl << endl << endl;
    cout << "Enter the number of items to sort: ";
    int num; 
    cin >> num;
    while(cin.fail()) // while cin does not recieve an integer 
    {
        cin.clear();
        cin.ignore(1000, '\n');
        cout << "Invalid entry. Try again: "; // try again
        cin >> num;
    }

    int array1[num], array2[num], array3[num], array4[num]; // initialize arrays 

    int randNum, sizeOfArray = sizeof(array1)/sizeof(array1[0]); // random number, size of the arrays 
    srand(time(NULL)); // random seed (used with rand()) 

    for(int i = 0; i < sizeOfArray; i++) // traverse through the array
    {
        randNum = rand() % 2147483647+1; // establish random number (from 1 to 2147483647)
        array1[i] = array2[i] = array3[i] = array3[i] = randNum; // set randNum to all arrays at current index
    }

    time_t beginTime, endTime; 
    double elapsedTime;

    cout << endl << "Elapsed time:" << endl << "\tInsertion Sort-\t";

    time(&beginTime);
    insertionSort(array1, sizeOfArray);
    time(&endTime);

    elapsedTime = difftime(endTime, beginTime);
    cout << elapsedTime << " seconds" << endl << "\tBubble Sort-\t";

    time(&beginTime);
    bubbleSort(array2, sizeOfArray);
    time(&endTime);

    elapsedTime = difftime(endTime, beginTime);
    cout << elapsedTime << " seconds" << endl << "\tMerge Sort-\t";

    time(&beginTime);
    mergeSort(array3, 0, sizeOfArray-1, sizeOfArray);
    time(&endTime);

    elapsedTime = difftime(endTime, beginTime);
    cout << elapsedTime << " seconds"<< endl; 





/* ********************* TESTING *************************
// *******************************************************

    cout << "Insertion->Unsorted:\t";
    for(int i = 0; i < sizeOfArray; i++)
    {
        cout <<  array1[i] << " ";
    }
    cout << endl;

    insertionSort(array1, sizeOfArray);

    cout << "Insertion->Sorted:\t";
    for(int i = 0; i < sizeOfArray; i++)
    {
        cout <<  array1[i] << " ";
    }
    cout << endl;




    cout << "Bubble->Unsorted:\t";
    for(int i = 0; i < sizeOfArray; i++)
    {
        cout <<  array2[i] << " ";
    }
    cout << endl;

    bubbleSort(array2, sizeOfArray);

    cout << "Bubble->Sorted:\t\t";
    for(int i = 0; i < sizeOfArray; i++)
    {
        cout <<  array2[i] << " ";
    }
    cout << endl;




    cout << "Merge->Unsorted:\t";
    for(int i = 0; i < sizeOfArray; i++)
    {
        cout <<  array3[i] << " ";
    }
    cout << endl;

    mergeSort(array3, 0, sizeOfArray-1, sizeOfArray);

    cout << "Merge->Sorted:\t\t";
    for(int i = 0; i < sizeOfArray; i++)
    {
        cout <<  array3[i] << " ";
    }
    cout << endl; */

    return 0;
}

void insertionSort(int array[], int size)
{
    for(int i = 1; i < size; i++)
    {
        int item = array[i], index = i;
        while(index > 0 && array[index-1] > item)
        {
            array[index] = array[index-1];
            index--;
        }
        array[index] = item;
    }
}

void bubbleSort(int array[], int size)
{
    bool sorted = false;
    for(int i = 1; i < size && !sorted; i++)
    {
        sorted = true;
        for(int i2 = 0; i2 < size-i; i2++)
        {
            int nextI = i2+1;
            if(array[i2] > array[nextI])
            {
                swap(array[i2], array[nextI]);
                sorted = false;
            }
        }
    }
}

void merge(int array[], int first, int mid, int last, int size)
{
    int tempArray[size];
    int first1 = first, first2 = mid+1;
    int last1 = mid, last2 = last;
    int index = first1;

    while(first1 <= last1 && first2 <= last2)
    {
        if(array[first1] < array[first2])
        {
            tempArray[index] = array[first1];
            first1++;
        }
        else
        {
            tempArray[index] = array[first2];
            first2++;
        }
        index++;
    }
    while(first1 <= last1)
    {
        tempArray[index] = array[first1];
        first1++;
        index++;
    }
    while(first2 <= last2)
    {
        tempArray[index] = array[first2];
        first2++;
        index++;
    }

    for(index = first; index <= last; index++)
    {
        array[index] = tempArray[index];
    }
}

void mergeSort(int array[], int first, int last, int size)
{
    if(first < last)
    {
        int mid = (first+last)/2;
        mergeSort(array, first, mid, size);
        mergeSort(array, mid+1, last, size);
        merge(array, first, mid, last, size);
    }
}

任何帮助是极大的赞赏.它可能是我系统的内存限制？我真的不知道大声笑只是一个想法.

Answer 1

您无法在具有固定有限大小的堆栈上分配此类大型数组,请尝试:

int* array1 = new int[num];