c/c++ 经典面试题

Posted 2020-06-17

char * mystrcpy(char *strDest, const char *strSrc)
{
    assert(strDest != NULL && strSrc != NULL);

    char *temp = strDest;
    while ( (*strDest++ = *strSrc++) != ‘\0‘ )
        NULL;

    return temp;
}

int mystrlen(const char *str)
{
    assert(str != NULL);
    int len = 0;
    while ( *str++ != ‘\0‘ )
    {
        len++;
    }

    return len;
}

void BubbleSort(vector<int> &data)
{
    int count = data.size();
    bool tag = false;

    for ( int i = 0; i < count; i++ )
    {
        tag = false;
        for ( int j = 0; j < count-i-1; j++ )
        {
            if ( data[j] > data[j+1] )
            {
                tag = true;
                int temp = data[j];
                data[j] = data[j+1];
                data[j+1] = temp;
            }
        }

        if ( !tag )
        {
            break;
        }
    }
}

void QuickSort( vector<int> &data, int left, int right )
{
    if ( left < right )
    {
        int index = data[left];
        int low = left;
        int high = right;

        while ( low < high )
        {
            while ( low < high && index < data[high] ) high--;
            data[low] = data[high];
            while ( low < high && index > data[low] ) low++;
            data[high] = data[low];
        }

        data[low] = index;

        QuickSort(data, left, low-1);
        QuickSort(data, low+1, right);
    }
}


void SelectSort( vector<int> &data )
{
    int count = data.size();
    for ( int i = 0; i < count; i++ )
    {
        int min = data[i]; 
        int index = i;
        for ( int j = i+1; j < count; j++ )
        {
            if ( min > data[j] )
            {
                min = data[j];
                index = j;
            }
        }

        if ( i != index )
        {
            int temp = data[i];
            data[i] = data[index];
            data[index] = temp;
        }
    }
}

class String
{
public:
    String(const char *str = NULL);
    String(const String &other);
    virtual ~String(void);
    String & operator =(const String &other);

private:
    char *m_data;
};

String::String(const char *str)
{
    if ( str == NULL )
    {
        m_data = new char[1];
        m_data[0] = ‘\0‘;
    } else
    {
        m_data = new char[strlen(str)+1];
        if ( m_data != NULL )
        {
            strcpy(m_data, str);
        }
    }
}

String::String(const String &other)
{
    m_data = new char[strlen(other.m_data)+1];
    if ( m_data != NULL )
    {
        strcpy(m_data, other.m_data);
    }
}

String::~String(void)
{
    if ( m_data != NULL )
    {
        delete[] m_data;
    }
}

String& String::operator=(const String &other)
{
    if ( this == &other )
    {
        return *this;
    } 

    delete[] m_data;

    m_data = new char[strlen(other.m_data)+1];
    if ( m_data != NULL )
    {
        strcpy(m_data, other.m_data);
    }

    return *this;
}