51 nod 1522 上下序列——序列dp

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define ll long long
using namespace std;
const int N=40,M=105;
int n,m,x[M],y[M],sgn[M],tx,ty;
ll dp[N][N<<1],ans;
char ch[20];
bool check(int p0,int p1,int r,int fx)
{
    //printf("p0=%d p1=%d r=%d fx=%d\n",p0,p1,r,fx);
    for(int i=1;i<=m;i++)
        if(sgn[i]==0&&
           ( ( (x[i]==p0||x[i]==p1)&&y[i]!=p0&&y[i]!=p1)||
             ( (y[i]==p0||y[i]==p1)&&x[i]!=p0&&x[i]!=p1) ) )
            return 0;//以前都合法，不合法仅出现在p0、p1位置上
    if(!fx)
    {
        for(int i=1;i<=m;i++)
        {
            //printf("sgn[%d]=%d\n",i,sgn[i]);
            if(sgn[i]==1||sgn[i]==2)
            {
                tx=x[i];ty=y[i];
                if(sgn[i]==2)swap(tx,ty);
                //printf("tx=%d ty=%d p0=%d p1=%d r=%d\n",tx,ty,p0,p1,r);
                if((ty==p0||ty==p1)&&tx>=p0&&tx<r) return 0;
            }
            if(sgn[i]==3||sgn[i]==4)
            {
                tx=x[i];ty=y[i];
                if(sgn[i]==4)swap(tx,ty);
                if((ty==p0||ty==p1)&&tx>p1&&tx<r) return 0;
            }
        }
    }
    if(fx==1)
    {
        for(int i=1;i<=m;i++)
        {
            if(sgn[i]==1||sgn[i]==2)
            {
                tx=x[i];ty=y[i];
                if(sgn[i]==2)swap(tx,ty);
                if((ty==p0||ty==p1)&&tx<=p1&&tx>r) return 0;
            }
            if(sgn[i]==3||sgn[i]==4)
            {
                tx=x[i];ty=y[i];
                if(sgn[i]==4)swap(tx,ty);
                if((ty==p0||ty==p1)&&tx<p0&&tx>r) return 0;
            }
        }
    }
    if(fx==2)
    {
        for(int i=1;i<=m;i++)
        {
            if(sgn[i]==1||sgn[i]==2)
            {
                tx=x[i];ty=y[i];
                if(sgn[i]==2)swap(tx,ty);
                if((ty==p0||ty==p1)&&tx>=p0&&tx<=p1) return 0;
            }
            if(sgn[i]==3||sgn[i]==4)
            {
                tx=x[i];ty=y[i];
                if(sgn[i]==4)swap(tx,ty);
                if((ty==p0||ty==p1)&&tx>p0&&tx<p1) return 0;
            }
        }
    }
    return 1;
}
int main()
{
    scanf("%d%d",&n,&m);ch[0]=getchar();
    while(ch[0]!=‘\n‘)ch[0]=getchar();
    for(int i=1,len=0,j;i<=m;i++,len=0)
    {
        ch[++len]=getchar();
        while(ch[len]!=‘\n‘)ch[++len]=getchar();
        for(j=1;j<len;j++)
        {
            if(ch[j]>=‘0‘&&ch[j]<=‘9‘)
                x[i]=(x[i]<<3)+(x[i]<<1)+ch[j]-‘0‘;
            else break;
        }
        while(ch[j]==‘ ‘)j++;
        //printf("j=%d chj=(%c)\n",j,ch[j]);
        if(ch[j]==‘=‘) sgn[i]=0,j++;
        else if(ch[j]==‘<‘&&ch[j+1]==‘=‘)sgn[i]=3,j+=2;
        else if(ch[j]==‘>‘&&ch[j+1]==‘=‘)sgn[i]=4,j+=2;
        else if(ch[j]==‘<‘)sgn[i]=1,j++;
        else if(ch[j]==‘>‘)sgn[i]=2,j++;
        while(ch[j]==‘ ‘)j++;
        //printf("j=%d chj=(%c)\n",j,ch[j]);
        for(;j<len;j++)
            y[i]=(y[i]<<3)+(y[i]<<1)+ch[j]-‘0‘;
        //printf("x=%d sgn=%d y=%d\n",x[i],sgn[i],y[i]);
    }
    dp[0][0]=1;
    for(int i=0,lm;i<n;i++)
    {
        lm=(i<<1);
        for(int j=0,r;j<=lm;j++)
        {
            //if(dp[i][j])printf("dp[%d][%d]=%lld\n",i,j,dp[i][j]);
            r=(n<<1)-(lm-j)+1;
            if(check(j+1,j+2,r,0))
                dp[i+1][j+2]+=dp[i][j];
                    //printf("dp[%d][%d]=%lld(%d,%d)\n",i+1,j+2,dp[i+1][j+2],i,j);
            if(check(r-2,r-1,j,1))
                dp[i+1][j]+=dp[i][j];
            //printf("dp[%d][%d]=%lld(%d,%d)\n",i+1,j,dp[i+1][j],i,j);
            if(check(j+1,r-1,0,2))
                dp[i+1][j+1]+=dp[i][j];
                    //printf("dp[%d][%d]=%lld(%d,%d)\n",i+1,j+1,dp[i+1][j+1],i,j);
        }
    }
    int lm=(n<<1);
    for(int j=0;j<=lm;j++) ans+=dp[n][j];
    printf("%lld\n",ans/3);
    return 0;
}