URAL 1519 Formula 1

第一个插头DP，看了CDQ的论文看的一知半解，更不要说些代码了。真的写不来啊。orz orz orz

参考的这位大神：http://hi.baidu.com/longmenwaideyu/item/0a11a033eb04db92b80c038c

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
const int maxn = 15;
const int HASH = 30007;
const int SIZE = 1000010;
typedef long long LL;
int N,M,maze[maxn][maxn],code[maxn],ch[maxn],ex,ey;
char b[maxn];

struct Hashmap{
    int e,first[HASH],next[SIZE];
    LL state[SIZE],f[SIZE];

    void init(){
        e = 0;
        memset(first,-1,sizeof(first));
    }

    void push(LL st,LL ans){
        int h = st%HASH;
        for(int i = first[h];i != -1;i = next[i])
        if(state[i] == st){
            f[i] += ans;
            return;
        }
        state[e] = st;
        f[e] = ans;
        next[e] = first[h];
        first[h] = e++;
    }
}dp[2];

void update(int *code,int len){
    for(int i = len;i >= 1;i--)
        code[i] = code[i-1];
    code[0] = 0;
}

void decode(int *code,int len,LL st){
    for(int i = len;i >= 0;i--){
        code[i] = st&7;
        st >>= 3;
    }
}

LL encode(int *code,int len){
    int cnt = 1;
    memset(ch,-1,sizeof(ch));
    ch[0] = 0;
    LL st = 0;
    for(int i = 0;i <= len;i++){
        if(ch[code[i]] == -1){
            ch[code[i]] = cnt++;
        }
        code[i] = ch[code[i]];
        st <<= 3;
        st |= code[i];
    }
    return st;
}

void dpblank(int i,int j,int now,int pre){
    int left,up,t;
    for(int k = 0;k < dp[pre].e;k++){
        decode(code,M,dp[pre].state[k]);
        left = code[j-1],up = code[j];

        if(left && up){
            if(left == up){
                if(i == ex && j == ey){
                    code[j-1] = code[j] = 0;
                    if(j == M)  update(code,M);
                    dp[now].push(encode(code,M),dp[pre].f[k]);
                }
            }
            else{
                code[j-1] = code[j] = 0;
                for(t = 0;t <= M;t++){
                    if(code[t] == up)   code[t] = left;
                }
                if(j == M)  update(code,M);
                dp[now].push(encode(code,M),dp[pre].f[k]);
            }
        }else if((!left && up) ||(left && !up)){
            if(left) t = left;
            else    t = up;
            if(maze[i][j+1]){
                code[j-1] = 0,code[j] = t;
                dp[now].push(encode(code,M),dp[pre].f[k]);
            }
            if(maze[i+1][j]){
                code[j-1] = t,code[j] = 0;
                if(j == M)  update(code,M);
                dp[now].push(encode(code,M),dp[pre].f[k]);
            }
        }else{
            if(maze[i+1][j] && maze[i][j+1]){
                code[j-1] = code[j] = 13;
                dp[now].push(encode(code,M),dp[pre].f[k]);
            }
        }
    }
}

void dpblock(int i,int j,int now,int pre){
    for(int k = 0;k < dp[pre].e;k++){
        decode(code,M,dp[pre].state[k]);
        code[j-1] = code[j] = 0;
        if(j == M)  update(code,M);
        dp[now].push(encode(code,M),dp[pre].f[k]);
    }
}

int main()
{
    while(scanf("%d%d",&N,&M) != EOF){
        memset(maze,0,sizeof(maze));
        ex = 0;
        for(int i = 1;i <= N;i++){
            scanf("%s",b+1);
            for(int j = 1;j <= M;j++)
                if(b[j] == '.') maze[ex=i][ey=j] = 1;
        }
        if(ex == 0){
            printf("0
");
            continue;
        }
        int now = 0,pre = 1;
        dp[now].init();
        dp[now].push(0,1);
        for(int i = 1;i <= N;i++){
            for(int j = 1;j <= M;j++){
                swap(now,pre);
                dp[now].init();
                if(maze[i][j])  dpblank(i,j,now,pre);
                else            dpblock(i,j,now,pre);
            }
        }
        LL ans = 0;
        for(int i = 0;i < dp[now].e;i++)
            ans += dp[now].f[i];
        printf("%I64d
",ans);
    }
    return 0;
}