"Bzoj 1345" [Baltic2007] sequence problem sequence

1345: [Baltic2007] sequence problem sequence time limit: 5 Sec Memory Limit: 162 MB
Submit: 618 Solved: 307
[Submit] [Status] [Discuss] Description for a given sequence A1, ..., an, we do an operation on it. reduce (i), which replaces the elements AI and ai+1 in the sequence with an element, Max (ai,ai+1), to get a new sequence shorter than the original sequence. The cost of this operation is Max (ai,ai+1). After n-1 the operation, you can get a sequence of length 1. Our task is to calculate the lowest cost of the reduce operation step, turning the given sequence into a sequence of length 1. Input first behaves as an integer n (1 <= n <= 1,000,000) representing the length of a given sequence. The next n rows, one integer for each line of AI (0 <=ai<= 1, 000, 000, 000), are the elements in the sequence. Output has only one row, an integer, and the minimum cost of turning the sequence into an element. Sample Input3
1
2
3Sample Output5

HINT

30% of test Data n<=500;
50% of the test data N <= 20,000.

Monotone queue.

Each number must be merged with the smaller of the first number on both sides of him that is larger than he, and the direct monotone queue O (n) does.

#include <iostream> #include <algorithm> #include <cstring> #include <cstdlib> #include < Cstdio> #define LL Long long#define inf 1000000005#define M 1000000+5using namespace Std;int a[m],q[m],n,s[m];int Main ( {    scanf ("%d", &n), for (int i=1;i<=n;i++) scanf ("%d", &a[i]), s[i]=inf;q[1]=a[1];int r=1;for (int i=2;i <=n;i++) {while (R>=1&&a[i]>q[r]) r--;if (R) s[i]=q[r];while (R>=1&&q[r]==a[i]) r--;q[++r ]=a[i];} r=1;q[1]=a[n];for (int i=n-1;i;i--) {while (R>=1&&a[i]>q[r]) r--;if (R) s[i]=min (S[i],q[r]), while (r> =1&&q[r]==a[i]) r--;q[++r]=a[i];} LL ans=0;for (int i=1;i<=n;i++) if (S[i]!=inf) Ans+=s[i];cout<<ans<<endl;return 0;}

"Bzoj 1345" [Baltic2007] sequence problem sequence