程式碼：

#include<bits/stdc++.h>
using namespace std;
const int inf = 1e9;
const int mm = 111111;
const int maxn = 2999;
int node,src,dest,edge;
int ver[mm],flow[mm],cst[mm],nxt[mm];
int head[maxn],work[maxn],dis[maxn],q[maxn];
int tot_cost;
void prepare(int _node,int _src,int _dest)
{
    node=_node,src=_src,dest=_dest;
    for(int i=0; i<node; ++i)head[i]=-1;
    edge=0;
    tot_cost = 0;
}
void add_edge(int u,int v,int c,int cost)
{
    ver[edge]=v,flow[edge]=c,nxt[edge]=head[u],cst[edge]=cost,head[u]=edge++;
    ver[edge]=u,flow[edge]=0,nxt[edge]=head[v],cst[edge]=-cost,head[v]=edge++;
}
int ins[maxn];
int pre[maxn];
bool Dinic_spfa()
{
	memset(ins,0,sizeof(ins));
	memset(dis,-1,sizeof(dis));
	memset(pre,-1,sizeof(pre));
	queue<int> Q;
    //int i,u,v,l,r=0;
    Q.push(src);
    dis[src] = 0,ins[src] = 1;
    pre[src] = -1;
    while(!Q.empty()){
    	int u = Q.front();Q.pop();
		ins[u] = 0;
		for(int e = head[u];e != -1;e = nxt[e]){
			int v = ver[e];
			if(!flow[e]) continue;
			if(dis[v] < 0 || dis[v] > dis[u] + cst[e]){
				dis[v] = dis[u] + cst[e];
				pre[v] = e;
				if(!ins[v]) ins[v] = 1,Q.push(v);
			}
		}    	
	}
    return dis[dest] != -1;
}
int Dinic_flow()
{
    int i,ret=0,delta=inf;
    while(Dinic_spfa())
    {
    	for(int i=pre[dest];i != -1;i = pre[ver[i^1]])
    		delta = min(delta,flow[i]);
		for(int i=pre[dest];i != -1;i = pre[ver[i^1]])
    		flow[i] -= delta,flow[i^1] += delta;
		ret+=delta;
		tot_cost += dis[dest]*delta;
    }
    return ret;
}
int abc[27];
int ag[111];
int val[111];
int n;
int main(){
	int sum = 0;
	scanf("%d",&n);
	prepare(1+26+n/2*26+n+1,0,1+26+n/2*26+n);
	for(int i = 1;i <= n;++i){
		char c;scanf(" %c",&c);
		abc[c-'a'+1]++;
		ag[i] = c-'a'+1;
	}
	for(int i = 1;i <= n;++i){
		scanf("%d",&val[i]);
		sum += val[i];
	}
	for(int i = 1;i <= 26;++i) add_edge(0,i,abc[i],0);
	for(int i = 1;i <= 26;++i){
		for(int j = 1;j <= n/2;j++){
			int _a = 26+(i-1)*n/2+j;
			add_edge(i,_a,1,0);
			int f1 = j,f2 = n-j+1;
			if(ag[f1] == i) add_edge(_a,f1+26+26*n/2,1,0);
			else add_edge(_a,f1+26+26*n/2,1,val[f1]);
			if(ag[f2] == i) add_edge(_a,f2+26+26*n/2,1,0);
			else add_edge(_a,f2+26+26*n/2,1,val[f2]);
		}
	}
	for(int i = 1;i <= n;++i) add_edge(26+26*n/2+i,1+26+n/2*26+n,1,0);
	int f = Dinic_flow();
	//cout<<f<<endl;
	cout<<sum - tot_cost<<endl;
	return 0;
}