joj1995

 1995: Energy

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ResultTIME LimitMEMORY LimitRun TimesAC TimesJUDGE3s10240K1336351Standard

Mr. Jojer is a very famous chemist. He is doing a research about behavior of a group of atoms. Atoms may have different energy and energy can be positive or negative or zero, e.g. 18 or -9. Absolute value of energy can not be more than 100. Any number of continuous atoms can form an atom-group. Energy of an atom-group is defined by the sum of energy of all the atoms in the group. All the atoms form an atom-community which is a line formed by all the atoms one by one. Energy of an atom-community is defined by the greatest energy of an atom-group that can be formed by atoms in the atom-community. The problem is, given an atom-community, to calculate its energy.

Input

The input contains several test cases. Each test case consists of two lines describing an atom-community. The first line of each test case contains an integer N(N<=1000000), the number of atoms in the atom-community. The second line of each test case contains N integers, separated by spaces, each representing energy of an atom, given in the order according to the atom-community. The last test case marks by N=-1, which you should not proceed.

Output

For each test case(atom-community description), print a single line containing the energy.

Sample Input

58 0 6 4 -1-1

Sample Output

18

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#include<iostream>
using namespace std;
int s[1000000+100];
int a[1000000+100];
int main()
{
    int n;
    while(cin>>n)
    {
        if(n==-1)break;
        for(int i=0;i<n;i++)
            cin>>a[i];
        s[0]=a[0];
        for(int i=1;i<n;i++)
        {
            if(s[i-1]<0||s[i-1]+a[i]<=0)
                s[i]=a[i];
            else s[i]=s[i-1]+a[i];
        }
        int max=s[0];
        for(int i=1;i<n;i++)
        {
            if(max<s[i])
                max=s[i];
        }
        cout<<max<<endl;
    }
    return 0;
}

这个是一个动态规划的题目当是s[i-1]<0或者s[i-1]+a[i]<=0的时候前i项的最大值就是啊a[i]，将其赋给s[i]。