poj 3280(Cheapest Palindrome)

#include<iostream>
#include<stdio.h>
#include<string.h>
using namespace std;
int add[26],det[26],dp[2020][2020]={0};
char str[2020];
int dfs(int x,int y)
{
    if(x>=y)return 0;
    if(str[x]==str[y])
    {
        if(!dp[x+1][y-1])dp[x+1][y-1]=dfs(x+1,y-1);
        return dp[x+1][y-1];
    }
    else
    {
        int t1,t2;
        if(!dp[x][y-1])dp[x][y-1]=dfs(x,y-1);
        t1=dp[x][y-1]+min(add[str[y]-'a'],det[str[y]-'a']);

        if(!dp[x+1][y])dp[x+1][y]=dfs(x+1,y);
        t2=dp[x+1][y]+min(add[str[x]-'a'],det[str[x]-'a']);
        return min(t1,t2);
    }
}
int main()
{
    int n,m;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        char ch[3];
        scanf("%s",str);
        for(int i=0;i<n;i++)
        {
            scanf("%s",ch);
            scanf("%d%d",&add[ch[0]-'a'],&det[ch[0]-'a']);
        }
        printf("%d\n",dfs(0,m-1));
        break;
    }
    return 0;
}