动态规划——子序列

#include<iostream>
#include<algorithm>
using namespace std;
int n,dp[100100][2],a[100100];
int main(){
cin>>n;
for(int i = 1;i <= n;i++) cin>>a[i];
dp[1][0] = dp[1][1] = 1;
for(int i = 2;i <= n;i++){
for(int j = 0;j <= 1;j++){
if(j == 0)
if(a[i] < a[i-1]) dp[i][j] = dp[i-1][j^1] + 1;
else dp[i][j] = dp[i-1][j];
else
if(a[i] > a[i-1]) dp[i][j] = dp[i-1][j^1] + 1;
else dp[i][j] = dp[i-1][j];
}
}
cout<<max(dp
[0],dp
[1]);
return 0;
}