插头DP模板

Posted 2021-02-12 luoyibujue

/*
插头dp模板
抄的GNAQ 的
括号表示法

*/
#include<cstdio>
#include<algorithm>
#include<cstring>
#include<iostream>
#include<queue>
#include<cmath>
#define ll long long
#define M 13
#define mmp make_pair
using namespace std;
int read() {
    int nm = 0, f = 1;
    char c = getchar();
    for(; !isdigit(c); c = getchar()) if(c == '-') f = -1;
    for(; isdigit(c); c = getchar()) nm = nm * 10 + c - '0';
    return nm * f;
}
const int hs = 299987;
int mp[M][M], ex, ey, now, last, bit[30], g[2][300010], tot[2], n, m;
ll ans, f[2][300010];

struct Note {
    int nxt, to;
} note[300010];
int head[300010], cnt = 0;

char s[M];

void insert(int x, ll v) {
    int key = x % hs;
    for(int i = head[key]; i; i = note[i].nxt) {
        if(g[now][note[i].to] == x) {
            f[now][note[i].to] += v;
            return;
        }
    }
    tot[now]++;
    g[now][tot[now]] = x;
    f[now][tot[now]] = v;

    note[++cnt].nxt = head[key];
    head[key] = cnt;
    note[cnt].to = tot[now];
}

void Dp() {
    now = 1, last = 0;
    tot[now] = 1;
    f[now][1] = 1;
    g[now][1] = 0;
    for(int i = 1; i <= n; i++) {
        for(int j = 1; j <= tot[now]; j++) g[now][j] <<= 2;
        for(int j = 1; j <= m; j++) {
            cnt = 0;
            memset(head, 0, sizeof(head));
            swap(now, last);
            tot[now] = 0;
            ll nowans;
            int nowsta, sd, sr;
            for(int k = 1; k <= tot[last]; k++) {
                nowsta = g[last][k], nowans = f[last][k];
                sd = (nowsta >> bit[j]) % 4, sr = (nowsta >> bit[j - 1]) % 4;
                if(!mp[i][j]) {
                    if(!sd && !sr) insert(nowsta, nowans);
                } else if(!sd && !sr) {
                    if(mp[i + 1][j] && mp[i][j + 1]) insert(nowsta + (1 << bit[j - 1]) + 2 * (1 << bit[j]), nowans);
                } else if(!sd && sr) {
                    if(mp[i + 1][j]) insert(nowsta, nowans);
                    if(mp[i][j + 1]) insert(nowsta - sr * (1 << bit[j - 1]) + sr * (1 << bit[j]), nowans);
                } else if(sd && !sr) {
                    if(mp[i + 1][j]) insert(nowsta - sd * (1 << bit[j]) + sd * (1 << bit[j - 1]), nowans);
                    if(mp[i][j + 1]) insert(nowsta, nowans);
                } else if(sd == 1 && sr == 1) {
                    int count = 1;
                    for(int l = j + 1; l <= m; l++) {
                        if((nowsta >> bit[l]) % 4 == 1) count++;
                        else if((nowsta >> bit[l]) % 4 == 2) count--;
                        if(!count) {
                            insert(nowsta - (1 << bit[l]) - (1 << bit[j]) - (1 << bit[j - 1]), nowans);
                            break;
                        }
                    }
                } else if(sd == 2 && sr == 2) {
                    int count = 1;
                    for(int l = j - 2; l >= 0; l--) {
                        if((nowsta >> bit[l]) % 4 == 1) count--;
                        else if((nowsta >> bit[l]) % 4 == 2) count++;
                        if(!count) {
                            insert(nowsta - 2 * (1 << bit[j]) - 2 * (1 << bit[j - 1]) + (1 << bit[l]), nowans);
                            break;
                        }
                    }
                } else if(sd == 1 && sr == 2) {
                    insert(nowsta - 2 * (1 << bit[j - 1]) - (1 << bit[j]), nowans);
                } else if(sd == 2 && sr == 1) {
                    if(i == ex && j == ey) ans += nowans;
                }
            }
        }
    }
}

int main() {
    n = read(), m = read();
    for(int i = 1; i <= n; i++) {
        scanf("%s", s + 1);
        for(int j = 1; j <= m; j++) {
            if(s[j] == '.') mp[i][j] = 1, ex = i, ey = j;
        }
    }
    for(int i = 1; i <= 25; i++) bit[i] = i << 1;
    Dp();
    cout << ans << '
';
    return 0;
}