51nod 1050 循环数组最大子段和 （dp）

http://www.51nod.com/onlineJudge/questionCode.html#problemId=1050&noticeId=13385

参考：http://blog.csdn.net/acdreamers/article/details/38760805

#include<cstdio>
#include<algorithm>
using namespace std;
typedef long long ll;

int n;
ll a[1000010];

ll work()
{
    ll temp=0,m=0;
    for(int i=0;i<n;i++)
    {
        temp+=a[i];
        if(temp<0) temp=0;
        if(m<temp) m=temp;
    }
    return m;
}
int main()
{
    int t;
    ll sum,sum1,sum2;
    scanf("%d",&t);
    while(t--)
    {
        sum=0;
        scanf("%d",&n);
        for(int i=0;i<n;i++)
        {
            scanf("%lld",&a[i]);
            sum+=a[i];
        }
        sum1=work();
        for(int i=0;i<n;i++)
            a[i]=-a[i];
        sum2=work();
       // printf("%lld %lld %lld\n",sum,sum1,sum2);
        sum=max(sum+sum2,sum1);
        printf("%lld\n",sum);
    }
    return 0;
}