DP专题练习 toasting

区间dp

#include<bits/stdc++.h>
using namespace std;
const int maxn=1e6+7;
const int N=1550;
int n;
int f[maxn];
int dp[N][N];
int main()
{
    freopen("toasting.in","r",stdin);
    freopen("toasting.out","w",stdout);
    scanf("%d",&n);
    for(int i=1;i<=n;i++){
        scanf("%d",&f[i]); 
    }
    for(int i=2;i<=n;++i){
        for(int j=i-1;j>0;j-=2){
            for(int k=j;k<i;k+=2){
                int ans=0;
                if(f[i]==f[k]){
                    ans=1;
                } 
                dp[j][i]=max(dp[j][i],dp[j][k-1]+dp[k+1][i-1]+ans);
            }
        }
    } 
    printf("%d",dp[1][n]);
    return 0;
}