bzoj4820

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表示高斯消元总写错。。。

注意，概率和期望高斯消元，我们消的时候，取一个fabs最大的就好，别用eps判了，re惨了。。

#include<cstdio>#include<cmath>#include<cstdlib>#include<algorithm>#include<cstring>#include<queue>using namespace std;const int N=305;  int n,m,pos[N]; int head[N*N],tot,to[N*N],pre[N*N];void addedge(int u,int v) {to[++tot]=v;pre[tot]=head[u];head[u]=tot;}    char s[N];int ch[N*N][2],cnt,dep[N*N],fail[N*N];inline int idx(char ch) {return ch=='T'? 0:1;}void get_fail(){    queue<int> q;    if (ch[0][0]) q.push(ch[0][0]);    if (ch[0][1]) q.push(ch[0][1]);    while (!q.empty())    {        int u=q.front();q.pop();        for (int i=0;i<=1;i++)         if (ch[u][i]==0) ch[u][i]=ch[fail[u]][i];        else fail[ch[u][i]]=ch[fail[u]][i],q.push(ch[u][i]);            }}double a[N][N],bin[N];void jump(int id) {    a[id][n+1]=-bin[m];    int x=pos[id];    while (x)     {        for (int i=head[x];i;i=pre[i]) a[to[i]][id]+=bin[m-dep[x]];        x=fail[x];    }}void gauss(int n){    for (int i=1;i<=n;i++)    {        int j=i;        for (int k=i+1;k<=n;k++) if (fabs(a[k][i])>fabs(a[i][i])) j=k;        if (i!=j) swap(a[i],a[j]);                 double tmp=a[i][i];        for (j=i;j<=n+1;j++) a[i][j]/=tmp;                 for (j=1;j<=n;j++) if (j!=i)        {            tmp=a[j][i];            for (int k=1;k<=n+1;k++) a[j][k]-=a[i][k]*tmp;        }    }}int main(){    scanf("%d%d",&n,&m);    bin[0]=1;for (int i=1;i<=m;i++) bin[i]=bin[i-1]*0.5;          for (int i=1;i<=n;i++)     {        scanf("%s",s+1);        int u=0,id;        for (int j=1;j<=m;j++)         {            id=idx(s[j]);            if (ch[u][id]==0) ch[u][id]=++cnt;            u=ch[u][id];dep[u]=j;addedge(u,i);        }        pos[i]=u;    }    get_fail();          for (int i=1;i<=n;i++) jump(i);    for (int i=1;i<=n;i++) a[n+1][i]=1.0;    a[n+1][n+2]=1.0;    gauss(n+1);    for (int i=1;i<=n;i++) printf("%.10lf\n",a[i][n+2]);    return 0;}

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