Question

我一直在下面的代码中得到分段错误（核心转储）。关于为什么会发生这种情况的任何想法。该代码旨在从文本文档中读取数字，将它们转换为整数，执行基数排序，并打印出数组。

#include <cstdlib>
#include <iostream>
#include <iomanip>
#include <fstream>
#include <string>
#include <time.h>
#include <sstream>

using namespace std;

int getMax(int arr[], int n)
{
    int max = arr[0];
    for (int i = 1; i < n; i++)
        if (arr[i] > max)
            max = arr[i];
    return max;
}

void countSort(int arr[], int n, int exp)
{
    int output[n];
    int i, count[10] = {0};
    for (i = 0; i < n; i++)
        count[(arr[i] / exp) % 10]++;
    for (i = 1; i < 10; i++)
        count[i] += count[i - 1];
    for (i = n - 1; i >= 0; i--)
    {
        output[count[(arr[i] / exp) % 10] - 1] = arr[i];
        count[(arr[i] / exp) % 10]--;
    }
    for (i = 0; i < n; i++)
        arr[i] = output[i];
}

void radixsort(int arr[], int n)
{
    clock_t clockStart;
    clockStart = clock();

    int m = getMax(arr, n);
    for (int exp = 1; m / exp > 0; exp *= 10)
        countSort(arr, n, exp);

    cout << "\nTime taken by radix sort: " << (double)(clock() - clockStart) / CLOCKS_PER_SEC << endl;
}

int StrToInt(string sti) 
{
    int f;
    stringstream ss(sti); //turn the string into a stream
    ss >> f;
    return f;
}

int main()
{
    int arr[10000];
    int i = 0;
    int result;
    string line = "";

    ifstream myfile;
    myfile.open("integers2.txt");
    if(myfile.is_open())
    {
        while(!myfile.eof())
        {
            getline(myfile, line);
            result = StrToInt(line);
            arr[i] = result;
            //cout<< arr[i] <<"\n";
            i++;
        }
    }


    int n = sizeof(arr)/sizeof(arr[0]);
    radixsort(arr, n);

    for (int i = 0; i < n; i++)
    {
        cout << arr[i] << "\n";
    }

    return 0;
}

我用于输入的文本文件的内容： 1244 3455 6565 55 765 8768 687 879

Answer 1

您的程序具有未定义的行为，因为它使用的数组条目多于您使用数据初始化的数组。您为... declare OPTSARGS OPTSARGS=$(getoptp -o wh --long nopager,help -n myScript-- "$@") status=$? if ((status != 0)) then printf '%s\n' "$(sed '0,/^__USAGE__$/d' $0)" exit $status fi eval set -- "$OPTSARGS" while true do case "$1" in -w) diffargs="$diffargs -w"; shift;; --nopager) pager=cat; shift;; --) shift; break ;; ## end of opts, remaining $*, if any, are args -h | --help) printf '%s\n' "$(sed '0,/^__USAGE__$/d' $0)" exit 0;; *) echo "Internal error!" printf '%s\n' "$(sed '0,/^__USAGE__$/d' $0)" exit 1;; esac done ... echo "Done" exit 0 __USAGE__ myScript [-w] [--nopager] [file [file...] ] Some description goes here. -w - Do not compare whitespace --nopager - Do not pass the output through 'less'传递整个数组的长度，即使其中只有一小部分（n到0）已初始化。

更改代码以在读取循环中使用i代替n，并将未修改的i传递给sort函数。这将解决问题（demo）。

Answer 2

这是您的工作代码：

#include <cstdlib>
#include <iostream>
#include <iomanip>
#include <fstream>
#include <string>
#include <time.h>
#include <sstream>

using namespace std;

int getMax(int arr[], int n)
{
    int max = arr[0];
    for (int i = 1; i < n; i++)
        if (arr[i] > max)
            max = arr[i];
    return max;
}

void countSort(int arr[], int n, int exp)
{
    int output[n];
    int i, count[10] = {0};
    for (i = 0; i < n; i++)
        count[(arr[i] / exp) % 10]++;
    for (i = 1; i < 10; i++)
        count[i] += count[i - 1];
    for (i = n - 1; i >= 0; i--)
    {
        output[count[(arr[i] / exp) % 10] - 1] = arr[i];
        count[(arr[i] / exp) % 10]--;
    }
    for (i = 0; i < n; i++)
        arr[i] = output[i];
}

void radixsort(int arr[], int n)
{
    clock_t clockStart;
    clockStart = clock();

    int m = getMax(arr, n);
    for (int exp = 1; m / exp > 0; exp *= 10)
        countSort(arr, n, exp);

    cout << "\nTime taken by radix sort: " << (double)(clock() - clockStart) / CLOCKS_PER_SEC << endl;
}

int StrToInt(string sti) 
{
    int f;
    stringstream ss(sti); //turn the string into a stream
    ss >> f;
    return f;
}

int main()
{
    const int MAX_SIZE = 10;

    int arr[ MAX_SIZE ] = { 0 };

    //int i = 0;
    //int result = 0;
    string line = "";

    ifstream myfile;
    myfile.open("integers2.txt");
    if(!myfile.is_open())
    {
        cerr << "Could not open file!\n";
        return -1;
    }

    cout << "Reading integers...\n";

    int index = 0;
    //while ( index < SIZE && getline( myfile, line ) )
    while ( index < MAX_SIZE && myfile >> arr[ index ] )
    {
        //getline( myfile, line );
        //result = StrToInt( line );
        //arr[index] = std::stoi( line );
        cout << arr[index] <<"\n";
        index++;
    }

    cout << "Sorting integers...\n";

    //int n = sizeof(arr) / sizeof(arr[0]);

    radixsort( arr, index );

    for ( int i = 0; i < index; i++ )
    {
        cout << arr[i] << "\n";
    }

    return 0;
}

有些观点：

检查std::stoi是否有字符串转换为整数;顺便说一句，你不需要这样做。请直接阅读：while ( file >> integer )。
需要检查文件是否已打开;否则返回ERROR;在你的情况下，即使文件没有打开，代码的其余部分仍在执行，即if ( myfile.open() ) { ... }之后的代码
while( !myfile.eof() )是不好的做法。请参阅：Why is iostream::eof inside a loop condition considered wrong?
您不需要像int n = sizeof(arr) / sizeof(arr[0]);那样计算尺寸，因为您已经知道尺寸。只需使用const即可。
从文件中读取时，还需要验证阵列的最大大小。您应该阅读尺寸允许的内容。处理out-of-bounds读/写错误。
使用<ctime>代替<time.h>。

继续得到分段错误？

2 个答案: