51nod1050(最大子序列和)

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题意：求循环数组的最大子序列和

代码：

#include <iostream>using namespace std;long long num[100005];int main(){    long long n,i,sum1,sum2,summ,maxx,maxx1,maxx2;    while(cin>>n)    {        sum1=sum2=summ=maxx1=maxx2=0;        for(i=1;i<=n;i++)        {            cin>>num[i];                           sum1+=num[i];            if(sum1<0)            sum1=0;            else if(sum1>maxx1)            maxx1=sum1;            summ+=num[i];            sum2-=num[i];            if(sum2<0)            sum2=0;            else if(sum2>maxx2)            maxx2=sum2;                 //同时求出最大子序列和和最小子序列和        }        //cout<<maxx1<<" "<<summ<<" "<<maxx2<<endl;        maxx=max(maxx1,summ+maxx2);        cout<<maxx<<endl;    }    return 0;}