面试题22：栈的压入，弹出序列

注意判断条件：

bool IsPopOrder(const int* pPush, const int* pPop, int nLength)
{
    bool bPossible = false;

    if(pPush != NULL && pPop != NULL && nLength > 0)
    {
        const int* pNextPush = pPush;
        const int* pNextPop = pPop;

        std::stack<int> stackData;

        while(pNextPop - pPop < nLength)
        {
            // 当辅助栈的栈顶元素不是要弹出的元素
            // 先压入一些数字入栈
            while(stackData.empty() || stackData.top() != *pNextPop)
            {
                // 如果所有数字都压入辅助栈了，退出循环
                if(pNextPush - pPush == nLength)
                    break;

                stackData.push(*pNextPush);

                pNextPush ++;
            }

            if(stackData.top() != *pNextPop)
                break;

            stackData.pop();
            pNextPop ++;
        }

        if(stackData.empty() && pNextPop - pPop == nLength)
            bPossible = true;
    }

    return bPossible;
}

 我的代码：

bool IsPopOrder(const int* pPush, const int* pPop, int nLength)
{
    if (pPush == NULL || pPop == NULL || nLength == 0)
        return false;

    const int *pNextPush = pPush;
    const int *pNextPop = pPop;

    std::stack<int> stackData;
    while (nLength != 0)
    {
        while (nLength != 0 && *pNextPush != *pNextPop)
        {
            stackData.push(*pNextPush);
            pNextPush++;
            nLength--;
        }
        if(nLength != 0)
        {
            stackData.push(*pNextPush);
            pNextPush++;
            nLength--;
        }
        while (stackData.size() > 0 && stackData.top() == *pNextPop)
        {
            stackData.pop();
            pNextPop++;
        }
    }
    if (stackData.empty())
        return true;
    else
        return false;

}