HDOJ 3622 - Bomb Game 2-sat+二分....细心...

       题意:

                 有N个炸弹..每个炸弹有两个位置可以选择..把炸弹放到其中一个地方去...炸弹的爆炸范围是其为圆心的圆...两个炸弹不能有攻击范围上的重合..问要满足条件..炸弹爆炸范围的半径最长能是多少...

       题解:

                 每个炸弹看成一类..其在两个中比选一个..符合2-sat的构图条件....那么就二分枚举炸弹的爆炸范围..枚举相互是否干扰来做边构造2-sat模型...tarjan来判断是否合法..

                 题目不难..但是我2B了...在初始化vector时..for (i=0;i<(n<<1);i++)  T[i].clear() 写成了for (i=0;i<(1<<n);i++)  T[i].clear()...搞得我查了好久的错误..还写了几个版本的代码..这道题不好自己出数据..搞得很郁闷..最后怀疑是vector使用的问题..就索性写了个链表..结果就A了~~再反过头来看..发现了错误的根源...弱啊......

Program-----链表存图..整个程序int型计算..结果再开方除2输出

#include<iostream>#include<stdio.h>#include<string.h>#include<cmath>#include<queue>#include<stack>#include<set>#include<map>#include<algorithm>#define ll long long#define oo 1000000007#define pi acos(-1.0)#define MAXN 205#define MAXM 100005using namespace std;struct node{       int x0,y0,x1,y1;}b[MAXN];struct LINE{       int x,y,next;}line[MAXM];int Lnum,_next[MAXN],dfn[MAXN],low[MAXN],tp[MAXN],tpnum,DfsIndex,arc[MAXN][MAXN];bool instack[MAXN];stack<int>  mystack;int dis(int x0,int y0,int x1,int y1){       return (x0-x1)*(x0-x1)+(y0-y1)*(y0-y1);}void addline(int x,int y){       line[++Lnum].next=_next[x],_next[x]=Lnum;       line[Lnum].x=x,line[Lnum].y=y;}void tarjan(int x)  {         int y,k;       dfn[x]=low[x]=++DfsIndex;         instack[x]=true;         mystack.push(x);         for (k=_next[x];k;k=line[k].next)       {                y=line[k].y;                if (!dfn[y])                {                    tarjan(y);                    low[x]=min(low[x],low[y]);                }else                     if (instack[y]) low[x]=min(low[x],dfn[y]);         }         if (dfn[x]==low[x])         {                tpnum++;                do                {                      x=mystack.top();                      mystack.pop();                      instack[x]=false;                      tp[x]=tpnum;                }while (dfn[x]!=low[x]);         }         return;  }  bool _2sat(int n,int d){       int i,j;        Lnum=0;       memset(_next,0,sizeof(_next));       for (i=0;i<n;i++)          for (j=i+1;j<n;j++)          {                     if (arc[i<<1][j<<1]<d)                      addline(i<<1,j<<1|1),addline(j<<1,i<<1|1);                  if (arc[i<<1][j<<1|1]<d)                      addline(i<<1,j<<1),addline(j<<1|1,i<<1|1);                  if (arc[i<<1|1][j<<1]<d)                      addline(i<<1|1,j<<1|1),addline(j<<1,i<<1);                  if (arc[i<<1|1][j<<1|1]<d)                      addline(i<<1|1,j<<1),addline(j<<1|1,i<<1);          }       memset(dfn,0,sizeof(dfn));       memset(instack,false,sizeof(instack));       while (!mystack.empty()) mystack.pop();       tpnum=DfsIndex=0;       for (i=0;i<(n<<1);i++)           if (!dfn[i]) tarjan(i);       for (i=0;i<n;i++)           if (tp[i<<1]==tp[i<<1|1]) return false;       return true;}int main(){       int n,i;          while (~scanf("%d",&n))       {                for (i=0;i<n;i++) scanf("%d%d%d%d",&b[i].x0,&b[i].y0,&b[i].x1,&b[i].y1);                for (i=0;i<n;i++)                  for (int j=i+1;j<n;j++)                  {                         arc[i<<1][j<<1]=arc[j<<1][i<<1]=dis(b[i].x0,b[i].y0,b[j].x0,b[j].y0);                         arc[i<<1][j<<1|1]=arc[j<<1|1][i<<1]=dis(b[i].x0,b[i].y0,b[j].x1,b[j].y1);                         arc[i<<1|1][j<<1]=arc[j<<1][i<<1|1]=dis(b[i].x1,b[i].y1,b[j].x0,b[j].y0);                         arc[i<<1|1][j<<1|1]=arc[j<<1|1][i<<1|1]=dis(b[i].x1,b[i].y1,b[j].x1,b[j].y1);                  }                int l,r,mid;                l=0,r=2*oo;                while (r-l>1)                {                        mid=(r+l)/2;                         if (_2sat(n,mid)) l=mid;                           else r=mid;                }                printf("%.2lf\n",sqrt(l)*0.5);       }       return 0;}

Program-----vector存图..其他同上

#include<iostream>#include<stdio.h>#include<string.h>#include<cmath>#include<queue>#include<stack>#include<set>#include<map>#include<algorithm>#define ll long long#define oo 1000000007#define pi acos(-1.0)#define MAXN 205using namespace std;struct node{       int x0,y0,x1,y1;}b[MAXN];vector<int> T[MAXN];int dfn[MAXN],low[MAXN],tp[MAXN],tpnum,DfsIndex,arc[MAXN][MAXN];bool instack[MAXN];stack<int>  mystack;int dis(int x0,int y0,int x1,int y1){       return (x0-x1)*(x0-x1)+(y0-y1)*(y0-y1);}void tarjan(int x)  {         int i,y,m=T[x].size();         dfn[x]=low[x]=++DfsIndex;         instack[x]=true;         mystack.push(x);         for (i=0;i<m;i++)         {                y=T[x][i];                if (!dfn[y])                {                    tarjan(y);                    low[x]=min(low[x],low[y]);                }else                     if (instack[y]) low[x]=min(low[x],dfn[y]);         }         if (dfn[x]==low[x])         {                tpnum++;                do                {                      x=mystack.top();                      mystack.pop();                      instack[x]=false;                      tp[x]=tpnum;                }while (dfn[x]!=low[x]);         }         return;  }  bool _2sat(int n,int d){       int i,j;       for (i=0;i<(n<<1);i++) T[i].clear(); //小错误..搞了N久才发现..        for (i=0;i<n;i++)          for (j=i+1;j<n;j++)          {                     if (arc[i<<1][j<<1]<d)                      T[i<<1].push_back(j<<1|1),T[j<<1].push_back(i<<1|1);                  if (arc[i<<1][j<<1|1]<d)                      T[i<<1].push_back(j<<1),T[(j<<1)|1].push_back(i<<1|1);                  if (arc[i<<1|1][j<<1]<d)                      T[(i<<1)|1].push_back((j<<1)|1),T[j<<1].push_back(i<<1);                  if (arc[i<<1|1][j<<1|1]<d)                      T[(i<<1)|1].push_back(j<<1),T[(j<<1)|1].push_back(i<<1);          }       memset(dfn,0,sizeof(dfn));       memset(instack,false,sizeof(instack));       while (!mystack.empty()) mystack.pop();       tpnum=DfsIndex=0;       for (i=0;i<(n<<1);i++)           if (!dfn[i]) tarjan(i);       for (i=0;i<n;i++)           if (tp[i<<1]==tp[i<<1|1]) return false;       return true;}int main(){       int n,i;        while (~scanf("%d",&n))       {                for (i=0;i<n;i++) scanf("%d%d%d%d",&b[i].x0,&b[i].y0,&b[i].x1,&b[i].y1);                for (i=0;i<n;i++)                  for (int j=i+1;j<n;j++)                  {                         arc[i<<1][j<<1]=arc[j<<1][i<<1]=dis(b[i].x0,b[i].y0,b[j].x0,b[j].y0);                         arc[i<<1][j<<1|1]=arc[j<<1|1][i<<1]=dis(b[i].x0,b[i].y0,b[j].x1,b[j].y1);                         arc[i<<1|1][j<<1]=arc[j<<1][i<<1|1]=dis(b[i].x1,b[i].y1,b[j].x0,b[j].y0);                         arc[i<<1|1][j<<1|1]=arc[j<<1|1][i<<1|1]=dis(b[i].x1,b[i].y1,b[j].x1,b[j].y1);                  }                int l,r,mid;                l=0,r=2*oo;                while (r-l>1)                {                       mid=(r+l)>>1;                        if (_2sat(n,mid)) l=mid;                           else r=mid;                }                printf("%.2f\n",sqrt(l)*0.5);       }       return 0;}

Program-----vector存图..直接浮点进行运算...

#include<iostream>#include<stdio.h>#include<string.h>#include<cmath>#include<queue>#include<stack>#include<set>#include<map>#include<algorithm>#define ll long long#define eps 1e-5#define oo 1000000007#define pi acos(-1.0)#define MAXN 205using namespace std;struct node{       int x0,y0,x1,y1;}b[MAXN];vector<int> T[MAXN];int dfn[MAXN],low[MAXN],tp[MAXN],tpnum,DfsIndex;double arc[MAXN][MAXN];bool instack[MAXN];stack<int>  mystack;double dis(int x0,int y0,int x1,int y1){       return sqrt((x0-x1)*(x0-x1)+(y0-y1)*(y0-y1));}void tarjan(int x)  {         int i,y,m=T[x].size();         dfn[x]=low[x]=++DfsIndex;         instack[x]=true;         mystack.push(x);         for (i=0;i<m;i++)         {                y=T[x][i];                if (!dfn[y])                {                    tarjan(y);                    low[x]=min(low[x],low[y]);                }else                     if (instack[y]) low[x]=min(low[x],dfn[y]);         }         if (dfn[x]==low[x])         {                tpnum++;                do                {                      x=mystack.top();                      mystack.pop();                      instack[x]=false;                      tp[x]=tpnum;                }while (dfn[x]!=low[x]);         }         return;  }  bool _2sat(int n,double d){       int i,j;       for (i=0;i<(n<<1);i++) T[i].clear();       for (i=0;i<n;i++)          for (j=i+1;j<n;j++)          {                     if (arc[i<<1][j<<1]+eps<d)                      T[i<<1].push_back(j<<1|1),T[j<<1].push_back(i<<1|1);                  if (arc[i<<1][j<<1|1]+eps<d)                      T[i<<1].push_back(j<<1),T[(j<<1)|1].push_back(i<<1|1);                  if (arc[i<<1|1][j<<1]+eps<d)                      T[(i<<1)|1].push_back((j<<1)|1),T[j<<1].push_back(i<<1);                  if (arc[i<<1|1][j<<1|1]+eps<d)                      T[(i<<1)|1].push_back(j<<1),T[(j<<1)|1].push_back(i<<1);          }       memset(dfn,0,sizeof(dfn));       memset(instack,false,sizeof(instack));       while (!mystack.empty()) mystack.pop();       tpnum=DfsIndex=0;       for (i=0;i<(n<<1);i++)           if (!dfn[i]) tarjan(i);       for (i=0;i<n;i++)           if (tp[i<<1]==tp[i<<1|1]) return false;       return true;}int main(){       int n,i;         while (~scanf("%d",&n))       {                for (i=0;i<n;i++) scanf("%d%d%d%d",&b[i].x0,&b[i].y0,&b[i].x1,&b[i].y1);                for (i=0;i<n;i++)                  for (int j=i+1;j<n;j++)                  {                         arc[i<<1][j<<1]=arc[j<<1][i<<1]=dis(b[i].x0,b[i].y0,b[j].x0,b[j].y0);                         arc[i<<1][j<<1|1]=arc[j<<1|1][i<<1]=dis(b[i].x0,b[i].y0,b[j].x1,b[j].y1);                         arc[i<<1|1][j<<1]=arc[j<<1][i<<1|1]=dis(b[i].x1,b[i].y1,b[j].x0,b[j].y0);                         arc[i<<1|1][j<<1|1]=arc[j<<1|1][i<<1|1]=dis(b[i].x1,b[i].y1,b[j].x1,b[j].y1);                  }                double l,r,mid;                l=0,r=2*oo;                while (r-l>eps)                {                        mid=(r+l)/2;                         if (_2sat(n,mid)) l=mid;                           else r=mid;                }                printf("%.2lf\n",l*0.5);       }       return 0;}