uva10534---Wavio Sequence

Wavio is a sequence of integers. It has some interestingproperties.

·  Wavio is of odd length i.e. L = 2*n+ 1.

·  The first (n+1) integers ofWavio sequence makes a strictly increasing sequence.

·  The last (n+1) integers of Waviosequence makes a strictly decreasing sequence.

·  No two adjacent integers are same in aWavio sequence.

For example 1, 2, 3, 4, 5, 4, 3, 2, 0 is an Waviosequence of length 9. But 1, 2, 3, 4, 5, 4, 3, 2, 2 is not avalid wavio sequence. In this problem, you will be given a sequence ofintegers. You have to find out the length of the longest Wavio sequence whichis a subsequence of the given sequence. Consider, the given sequence as :

1 2 3 2 1 2 3 4 32 1 5 4 1 2 3 2 2 1.

Here the longest Wavio sequence is : 1 2 3 4 5 4 3 2 1. So, the outputwill be 9.

Input

The input filecontains less than 75 test cases. The description of each test case isgiven below: Input is terminated by end of file.

Each set starts with a postiveinteger, N(1<=N<=10000). In next few lines there will be Nintegers.

Output

For each set of input print the length of longest waviosequence in a line.

# Sample Input                                  Output for Sample Input

 `10` `1 2 3 4 5 4 3 2 1 10` `19` `1 2 3 2 1 2 3 4 3 2 1 5 4 1 2 3 2 2 1` `5` `1 2 3 4 5` ` ` `9` `9` `1`

```#include

#include

using namespace std;#define N 10001int dp1[10001],dp2[10001],a[10001],b[10001];int t;void LIS(int dp[],int a[]){
int stack[N];
int top=0;
stack[top]=-99999999;
for(int i=1; i<=t; i++)
{
//如果a[i]>栈顶部元素，则压栈
if(a[i]>stack[top])
{
stack[++top]=a[i];
dp[i]=top;
}
//如果a[i]不大于栈顶部元素，则二分查找第一个比a[i]大的元素
else
{
int l=1,r=top;
while(l<=r)
{
int mid=(l+r)>>1;
if(a[i]>stack[mid])
{
l=mid+1;
}
else
r=mid-1;
}
//替换a[i]
stack[l]=a[i];
dp[i]=l;
}
}}int main(){
while(cin>>t)
{
for(int i=1;i<=t;i++)
{
cin>>a[i];
b[t-i+1]=a[i];
}
memset(dp1,0,sizeof(dp1));
memset(dp2,0,sizeof(dp2));
LIS(dp1,a);
LIS(dp2,b);
int maxx=-1,ans=0;
for(int i=1;i<=t;i++)
{
ans=min(dp1[i],dp2[t-i+1])*2-1;
if(ans>maxx)
{
maxx=ans;
}
}
cout<

<

}
return 0;}

```

#### 最新留言

[***.249.68.14]2022年05月22日 15时44分02秒

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