• HDOJ 3622


           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 100005
    using 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
    ",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 205
    using 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
    ",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 205
    using 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
    ",l*0.5);
           }
           return 0;
    }
    




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  • 原文地址:https://www.cnblogs.com/riskyer/p/3239056.html
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