ahu-497-最长起伏子序列

#include<cstdio>
#include<cmath>
#include<cstring>
#include<cstdlib>
#include<stack>
#include<set>
#include<queue>
#include<map>
#include<iostream>
#include<algorithm>
using namespace std;
int a[6000],b[6000];
int main()
{
int i,j,k,n;
while(scanf("%d",&n))
{
if(n==0)break;
for(i=1;i<=n;i++)scanf("%d",&a[i]);
int l1=1;
b[1]=a[1];
for(i=2;i<=n;i++)
{
if(l1%2!=0)
{
if(a[i]>b[l1]){l1++;b[l1]=a[i];}
else
if(a[i]<b[l1]){b[l1]=a[i];}
}
else
{
if(a[i]<b[l1]){l1++;b[l1]=a[i];}
else
if(a[i]>b[l1]){b[l1]=a[i];}
}
}
int l2=1;
b[1]=a[1];
for(i=2;i<=n;i++)
{
if(l2%2==0)
{
if(a[i]>b[l2]){l2++;b[l2]=a[i];}
else
if(a[i]<b[l2]){b[l2]=a[i];}
}
else
{
if(a[i]<b[l2]){l2++;b[l2]=a[i];}
else
if(a[i]>b[l2]){b[l2]=a[i];}
}
}
printf("%d\n",max(l1,l2));
}
return 0;
}