面试题27：连续子数组的最大和

注意：当函数输入无效时，返回为0，而子数组的和也有可能为0，为了区分，设置一个全局变量标记输入是否有效。

思路用下表说明：

代码：

#include "stdafx.h"
#include <iostream>
using namespace std;

bool bInvalidInput = false;//用全局变量标记是否为无效输入
//求连续子数组的最大和
int FindGreatestSumOfSubArray(int nArr[], int nLength)
{
    if (nArr == NULL || nLength <=0)
    {
		bInvalidInput = true;
		return 0;
    }

    int nGreatestSum = 0x80000000;//记录连续子数组的最大和,初始值设置为很小的负数
	int nCurrentSum = 0;
	for (int i=0; i<nLength; i++)
	{        
		if (nCurrentSum <= 0)
		{
            nCurrentSum = nArr[i];
		}
		else
		{
			nCurrentSum += nArr[i];
		}

		if (nCurrentSum > nGreatestSum)
		{
			nGreatestSum = nCurrentSum;
		}
	}
	return nGreatestSum;
}

int _tmain(int argc, _TCHAR* argv[])
{
	int nArr1[8] = {1, -2, 3, 10, -4, 7, 2, -5};
	int nGreatestSumOfSubArray1 = FindGreatestSumOfSubArray(nArr1, 8);
	if (!bInvalidInput)
	{
		cout << "连续子数组的最大和为：" << nGreatestSumOfSubArray1 << endl;
	}

	int nArr2[8] = {-1, -2, -3, -10, -4, -7, -2, -5};
	int nGreatestSumOfSubArray2 = FindGreatestSumOfSubArray(nArr2, 8);
	if (!bInvalidInput)
	{
		cout << "连续子数组的最大和为：" << nGreatestSumOfSubArray2 << endl;
	}
	return 0;
}

运行结果：