【POJ】3017 Cut the Sequence

 1 #include<cstdio>

 2 #define MAXN 100010

 3 #define MIN(a,b) ((a)<(b)?(a):(b))

 4 typedef __int64 LL;

 5 LL limit,a[MAXN],dp[MAXN];

 6 int n,Q[MAXN];

 7 LL DoIt()

 8 {

 9     LL sum;

10     int i,j,k,front,rear;

11     for(i=1;i<=n;i++)

12     {

13         if(a[i]>limit)

14             return -1;

15     }

16     sum=dp[0]=0;

17     front=0;

18     rear=-1;

19     for(i=k=1;i<=n;i++)

20     {

21         sum+=a[i];

22         for(;sum>limit;k++)

23             sum-=a[k];

24         for(;front<=rear&&Q[front]<k;front++);

25         for(;front<=rear&&a[Q[rear]]<=a[i];rear--);

26         Q[++rear]=i;

27         dp[i]=dp[k-1]+a[Q[front]];

28         for(j=front;j<rear;j++)

29             dp[i]=MIN(dp[i],dp[Q[j]]+a[Q[j+1]]);

30     }

31     return dp[n];

32 }

33 int main()

34 {

35     int i;

36     while(~scanf("%d%I64d",&n,&limit))

37     {

38         for(i=1;i<=n;i++)

39             scanf("%I64d",&a[i]);

40         printf("%I64d\n",DoIt());

41     }

42     return 0;

43 }