面试题31：连续子数组的最大和

/*题目：输入一个整型数组，数组里有正数也有负数，数组中一个或连续的多个整数组成一个子数组。求所有子数组的和的最大值。要求时间复杂度为O(n)。*/#include <iostream>using namespace std;bool g_InvalidInput = false;int FindGreatestSumofSubarrary(int a[], int n){    //处理无效输入    if(a == NULL || n <= 0)    {        g_InvalidInput = true;        return 0;    }    int CurrentSum = 0;    int MaxSum = 0x80000000;//-2147483648    int start = 0;    int end = 0;    //遍历数组    for(int i = 0; i < n; ++i)    {        if(CurrentSum <= 0)        {            CurrentSum = a[i];            start = i;        }else        {            CurrentSum += a[i];        }        if(CurrentSum > MaxSum)        {            MaxSum = CurrentSum;            end = i;        }    }    if(start <= end)    {        for(int k = start; k <= end; ++k)        cout << a[k] << " ";    }else    {        cout << a[end];    }    cout << endl;    cout << MaxSum << endl;    return MaxSum;}//=================测试代码================void Test(char *TestName, int a[], int n, int expectedresult, bool expectedflag){    if(TestName != NULL)    cout << TestName << " begins: " << endl;    int result = FindGreatestSumofSubarrary(a, n);    if(result == expectedresult && g_InvalidInput == expectedflag)    cout << "Passed!" << endl;    else    cout << "Failed!" << endl;}//===============测试用例=================void Test1(){    int data[] = {1, -2, 3, 10, -4, 7, 2, -5};    Test("Test1", data, sizeof(data) / sizeof(int), 18, false);}//全是负数void Test2(){    int data[] = {-2, -8, -1, -5, -9};    Test("Test2", data, sizeof(data) / sizeof(int), -1, false);}//全是正数void Test3(){    int data[] = {2, 8, 1, 5, 9};    Test("Test3", data, sizeof(data) / sizeof(int), 25, false);}//无效输入void Test4(){    Test("Test4", NULL, 0, 0, true);}int main(){    Test1();    Test2();    Test3();    Test4();    return 0;}