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POJ_2479_DP

http://poj.org/problem?id=2479

 

从前向后保存起点到每一点的最长串,从后向前保存尾点到每一点的最长串。

然后枚举中断点,找前后和最大值就行了。

 

#include<iostream>#include<cstdio>#define MIN -0x3f3f3f3f;using namespace std;int a[50005],lmax[50005],rmax[50005],n;int main(){    int T;    scanf("%d",&T);    while(T--)    {        scanf("%d",&n);        lmax[0] = MIN;        rmax[n+1] = MIN;        for(int i = 1;i <= n;i++)    scanf("%d",&a[i]);        int sum = 0;        for(int i = 1;i <= n;i++)        {            sum += a[i];            if(lmax[i-1] < sum)    lmax[i] = sum;            else    lmax[i] = lmax[i-1];            if(sum < 0)    sum = 0;        }        sum = 0;        for(int i = n;i >= 1;i--)        {            sum += a[i];            if(rmax[i+1] < sum)    rmax[i] = sum;            else    rmax[i] = rmax[i+1];            if(sum < 0)    sum = 0;        }        int maxx = MIN;        for(int i = 1;i < n;i++)    maxx = max(maxx,lmax[i]+rmax[i+1]);        printf("%d\n",maxx);    }    return 0;    }

 

POJ_2479_DP