poj3280 最小代价回文串



形成回文串的最小代价（代价1）

                   for(int k=1;k

1.         {  
2.             for(int i=0,j=k;j
3.             {  
4.                 dp[i][j]=0x3f3f3f3f;  
5.                 if(s[i]==s[j])  
6.                     dp[i][j]=dp[i+1][j-1];  
7.                 else  
8.                 {  
9.                     dp[i][j]=min(dp[i+1][j],dp[i][j]);  
10.                     dp[i][j]=min(dp[i][j-1] ,dp[i][j]);  
11.                 }  
12.             }  
13.         }  

#include
#include
#include
#include
#include
#include
#include
using namespace std;
#define PI 3.1415926535897932
#define E 2.718281828459045
#define INF 0x3f3f3f3f
#define mod 9973
#define N 70
typedef long long ll;
const int M=100005;
int n,m;
int sx,sy,sz;
char mp[M];
int pa[M],rankk[M];
int head[M*6],vis[M*6];
double dis[M][10];
//int g[5][5];
int lowcost[M],closet[M];
char st1[5050],st2[5050];
int len[M*6];
//pair a[M];
vector g[M];
int sum[2005];
int dp[2005][2005];
int add,rem;
struct node
{
    int st,s;
};
bool cmp(node a,node b)
{
    if(a.st!=b.st)
        return a.st     return a.s }
int month[13]= {0,31,59,90,120,151,181,212,243,273,304,334,0};
bool isrun(int year)
{
    if((year%4==0&&year%100!=0)||(year%400==0))
        return true;
    return false;
}

int main()
{
    int i,j;
    char c;
    while(~scanf("%d%d",&n,&m))
    {
        scanf("%s%*c",mp);
        for(i=0;i         {
            scanf("%c %d %d%*c",&c,&add,&rem);
            sum[(c-'a')]=min(add,rem);
        }
        int len=strlen(mp);
        memset(dp,0,sizeof(dp));
        for(int k=1;k         {
            i=0;
            for(j=k;j             {
                dp[i][j]=INF;
                if(mp[i]==mp[j])
                    dp[i][j]=dp[i+1][j-1];
                else{
                    dp[i][j]=min(dp[i][j],dp[i+1][j]+sum[mp[i]-'a']);
                    dp[i][j]=min(dp[i][j],dp[i][j-1]+sum[mp[j]-'a']);
                }
            }
        }
        printf("%d\n",dp[0][m-1]);
    }
    return 0;
}

记忆化搜索

int dfs(int l,int r)
{
    if(dp[l][r]!=-1)
        return dp[l][r];
    if(l>=r)
    {
        return dp[l][r]=0;
    }
    if(mp[l]==mp[r])
    {
        return dp[l][r]=dfs(l+1,r-1);
    }
    else{
        return dp[l][r]=min(dfs(l+1,r)+sum[mp[l]-'a'],dfs(l,r-1)+sum[mp[r]-'a']);
    }
}
int main()
{
    int i,j;
    char c;
    while(~scanf("%d%d",&n,&m))
    {
        scanf("%s%*c",mp);
        for(i=0;i         {
            scanf("%c %d %d%*c",&c,&add,&rem);
            sum[(c-'a')]=min(add,rem);
        }
        memset(dp,-1,sizeof(dp));
        printf("%d\n",dfs(0,m-1));
    }
    return 0;
}