在 Linux Mint 上，我使用运算符new分配内存：
int maxNummber = 1000000;
int* arr = new int[maxNumber];
当我运行我的代码时，我遇到了
flybird@flybird ~/cplusplus_study $ ./a.out
-412179
Segmentation fault
当我更改时maxNumber = 100，代码运行成功。
命令的结果free -m：
flybird@flybird ~/cplusplus_study $ free -m
total used free shared buffers cached
Mem: 2016 800 1216 0 158 359
-/+ buffers/cache: 283 1733
Swap: 2045 0 2045
这是实际的代码：
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <iostream>
#include <fstream>
#include <ctime>
#include <memory>
#include <string.h>
#include <iterator>
#include <cstdlib>
using namespace std;
class GenRandomNumber;
class BitMap
{
public:
BitMap(int n):maxNumer(n)
{
int length = 1 + n / BITSPERWORD;
pData = new int[length];
memset(pData, 0, length);
}
void set(int i)
{
pData[i>>SHIFT] |= 1<<(i & MASK); // i&MASK 相当于i%32
}
void clear(int i)
{
pData[i>>SHIFT] &= ~(1<<(i & MASK)); // i>>SHIFT 相当于 i/32
}
bool test(int i)
{
return pData[i>>SHIFT] & (1<<(i & MASK));
}
void sort(string inputFile, string outputFile)
{
ifstream read(inputFile.c_str());
ofstream write(outputFile.c_str());
int temp = 0;
while (read>>temp)
set(temp);
for (int i = 0; i < maxNumer; ++i)
{
if(test(i))
write<<i<<endl;
}
read.close();
write.close();
}
~BitMap()
{
delete []pData;
pData = NULL;
}
private:
int* pData;
int maxNumer;
enum{ SHIFT = 5, MASK = 0x1F, BITSPERWORD = 32};
};
class GenRandomNumber
{
public:
static GenRandomNumber* genInstance()
{
if(!mInstance.get())
mInstance.reset(new GenRandomNumber());
return mInstance.get();
}
void generate1(string fileName, int m, int maxNumber)
{
ofstream outFile(fileName.c_str());
int* arr = new int[maxNumber];
for(int i = 0; i < maxNumber; i++)
arr[i] = i;
int temp = 0;
for(int j = 0; j < m; j++)
{
temp = randomRange(j, maxNumber - 1);
cout<<temp<<endl;
swap(arr[j], arr[temp]);
}
copy(arr, arr + m, ostream_iterator<int>(outFile, "\n"));
delete []arr;
outFile.close();
}
void generate2(string fileName, int m, int maxNumber)
{
BitMap bitmap(maxNumber);
ofstream outFile(fileName.c_str());
int count = 0;
int temp;
while (count < m)
{
srand(time(NULL));
temp = randomRange(0, maxNumber);
cout<<temp<<endl;
if (!bitmap.test(temp))
{
bitmap.set(temp);
outFile<<temp<<endl;
count++;
}
}
outFile.close();
}
private:
GenRandomNumber(){};
GenRandomNumber(const GenRandomNumber&);
GenRandomNumber& operator=(const GenRandomNumber&);
int randomRange(int low, int high)
{
srand(clock()); // better than srand(time(NULL))
return low + (RAND_MAX * rand() + rand()) % (high + 1 - low);;
}
static auto_ptr<GenRandomNumber> mInstance;
};
auto_ptr<GenRandomNumber> GenRandomNumber::mInstance;
int main()
{
const int MAX_NUMBER = 1000000;
GenRandomNumber *pGen = GenRandomNumber::genInstance();
pGen->generate1("test.txt", MAX_NUMBER, MAX_NUMBER);
BitMap bitmap(MAX_NUMBER);
bitmap.sort("test.txt", "sort.txt");
return 0;
}