面试题31：连续字数组的最大和

当前面计算的和是负数时，就没必要再用前面的结果了，curSum就等于当前数字，另外一个比较关键的问题是maxSum初值为最大的负数，只有这样才能保证一个序列最大值为负数时的结果正确性

bool g_InvalidInput = false;

int FindGreatestSumOfSubArray(int *pData, int nLength)
{
    if((pData == NULL) || (nLength <= 0))
    {
        g_InvalidInput = true;
        return 0;
    }

    g_InvalidInput = false;

    int nCurSum = 0;
    int nGreatestSum = 0x80000000;
    for(int i = 0; i < nLength; ++i)
    {
        if(nCurSum <= 0)
            nCurSum = pData[i];
        else
            nCurSum += pData[i];

        if(nCurSum > nGreatestSum)
            nGreatestSum = nCurSum;
    }

    return nGreatestSum;
}