[HEOI2014]逻辑翻译(分治)

#include<iostream>
#include<cstdio>
using namespace std;
typedef long long ll;
const int N=(1<<21)+10;
double x;
int n,top,p[N];
char s[N];
inline int rd(){
    int x=0;char c=getchar();bool f=0;
    while(!isdigit(c)){if(c==‘-‘)f=1;c=getchar();}
    while(isdigit(c)){x=(x<<1)+(x<<3)+(c^48);c=getchar();}
    return f?-x:x;
}    
ll gcd(ll x,ll y){if(x<0)x=-x;if(y<0)y=-y;return y?gcd(y,x%y):x;}
struct fs{
    ll x,y;
    fs operator +(const fs &b)const{
        ll xx=x*b.y+y*b.x,yy=y*b.y*2;
        ll g=gcd(yy,xx);
        xx/=g;yy/=g;
        return fs{xx,yy};
    }
    fs operator -(const fs &b)const{
        ll xx=x*b.y-y*b.x,yy=y*b.y*2;
        ll g=gcd(yy,xx);
        xx/=g;yy/=g;
        return fs{xx,yy};
    } 
}dp[N];
void dfs(int num,int x){
    if(num>n)return;
    p[++top]=x|(1<<num-1);
    dfs(num+1,x|(1<<num-1));dfs(num+1,x);
}
int main(){
    n=rd();
    for(int i=0;i<(1<<n);++i){
      int o=0;scanf("%s%lf",s+1,&x);
      for(int j=1;j<=n;++j){
          o<<=1;o|=(s[j]==‘+‘?1:0);
      }
      if(x>0)dp[o].x=(int)(x*100+0.1);//因为要向0取整，所以要判断正负 
      else dp[o].x=(int)(x*100-0.1);
      dp[o].y=100;
      ll g=gcd(dp[o].x,dp[o].y);
      dp[o].x/=g;dp[o].y/=g;
    }
    for(int i=(1<<n-1);i>=1;i>>=1)
      for(int j=0;j<(1<<n);j+=(i<<1))
        for(int k=0;k<i;++k){
            fs x=dp[k+j],y=dp[k+i+j];
            dp[k+j]=y-x;dp[k+i+j]=x+y;       
        }
    for(int i=0;i<(1<<n);++i){
        int x=i,l=0,r=(1<<n)-1;
        while(l!=r){
            int mid=(l+r)>>1;
            if(x&1)r=mid;else l=mid+1;x>>=1;
        }
        if(l<i)swap(dp[l],dp[i]);
    }
    dfs(1,0);
    for(int i=0;i<(1<<n);++i){
        int x=p[i];
        if(!dp[x].x)continue;
        if(dp[x].y<0)dp[x].y=-dp[x].y,dp[x].x=-dp[x].x;
        if(dp[x].y!=1)
        printf("%lld/%lld ",dp[x].x,dp[x].y);
        else printf("%lld ",dp[x].x);
        for(int j=1;j<=n;++j)if(x&(1<<j-1))printf("x%d",j);
        printf("\n");
    }
    return 0;
}