POJ 2296 Map Labeler

二分答案 + 2-SAT验证，判断正方形是否相交写起来有点烦，思路还是挺简单的。

#include<cstdio>
#include<cstring>
#include<cmath>
#include<stack>
#include<queue>
#include<algorithm>
using namespace std;

const int maxn=1005;
struct Point
{
    double x,y;
}p[maxn];
int N;

stack<int>S;
vector<int>G[maxn];
vector<int>FG[maxn];
int Belong[maxn];
int flag[maxn];
int Block;

int left,right,mid,ans;

void init()
{
    for(int i=0; i<maxn; i++) G[i].clear();
    for(int i=0; i<maxn; i++) FG[i].clear();
    memset(Belong,0,sizeof Belong);
    memset(flag,0,sizeof flag);
    while(!S.empty()) S.pop();
    Block=0;
}

void addEdge(int x,int y)
{
    G[x].push_back(y);
    FG[y].push_back(x);
}

void dfs1(int now)
{
    flag[now]=1;
    for(int i=0; i<G[now].size(); i++)
        if(!flag[G[now][i]])
            dfs1(G[now][i]);
    S.push(now);
}

void dfs2(int now)
{
    Belong[now]=Block;
    for(int i=0; i<FG[now].size(); i++)
        if(!Belong[FG[now][i]])
            dfs2(FG[now][i]);
}

bool judge()
{
    for(int i=0; i<2*N; i++) if(!flag[i]) dfs1(i);
    while(!S.empty())
    {
        int Top=S.top();
        S.pop();
        if(!Belong[Top])
        {
            Block++;
            dfs2(Top);
        }
    }
    for(int i=0; i<N; i++)
        if(Belong[2*i]==Belong[2*i+1])
            return 0;
    return 1;
}

bool F(int p1,int p2,int f1,int f2)
{
    double leftTop_p1_x,leftTop_p1_y;
    double rightBottom_p1_x,rightBottom_p1_y;

    double leftTop_p2_x,leftTop_p2_y;
    double rightBottom_p2_x,rightBottom_p2_y;

    if(f1==0)
    {
        leftTop_p1_x=p[p1].x-1.0*mid/2;
        leftTop_p1_y=p[p1].y;

        rightBottom_p1_x=p[p1].x+1.0*mid/2;
        rightBottom_p1_y=p[p1].y-mid;
    }
    else
    {
        leftTop_p1_x=p[p1].x-1.0*mid/2;
        leftTop_p1_y=p[p1].y+mid;

        rightBottom_p1_x=p[p1].x+1.0*mid/2;
        rightBottom_p1_y=p[p1].y;
    }

    if(f2==0)
    {
        leftTop_p2_x=p[p2].x-1.0*mid/2;
        leftTop_p2_y=p[p2].y;

        rightBottom_p2_x=p[p2].x+1.0*mid/2;
        rightBottom_p2_y=p[p2].y-mid;
    }

    else
    {
        leftTop_p2_x=p[p2].x-1.0*mid/2;
        leftTop_p2_y=p[p2].y+mid;

        rightBottom_p2_x=p[p2].x+1.0*mid/2;
        rightBottom_p2_y=p[p2].y;
    }


    if(leftTop_p1_x<leftTop_p2_x&&leftTop_p2_x<rightBottom_p1_x
        && rightBottom_p1_y<leftTop_p2_y&&leftTop_p2_y<leftTop_p1_y) return 1;

    if(leftTop_p1_x<leftTop_p2_x&&leftTop_p2_x<rightBottom_p1_x
        && rightBottom_p1_y<rightBottom_p2_y&&rightBottom_p2_y<leftTop_p1_y) return 1;

    if(leftTop_p1_x<rightBottom_p2_x&&rightBottom_p2_x<rightBottom_p1_x
        && rightBottom_p1_y<leftTop_p2_y&&leftTop_p2_y<leftTop_p1_y) return 1;

    if(leftTop_p1_x<rightBottom_p2_x&&rightBottom_p2_x<rightBottom_p1_x
        && rightBottom_p1_y<rightBottom_p2_y&&rightBottom_p2_y<leftTop_p1_y) return 1;

    if(leftTop_p2_x<leftTop_p1_x&&leftTop_p1_x<rightBottom_p2_x
        && rightBottom_p2_y<leftTop_p1_y&&leftTop_p1_y<leftTop_p2_y) return 1;

    if(leftTop_p2_x<leftTop_p1_x&&leftTop_p1_x<rightBottom_p2_x
        && rightBottom_p2_y<rightBottom_p1_y&&rightBottom_p1_y<leftTop_p2_y) return 1;

    if(leftTop_p2_x<rightBottom_p1_x&&rightBottom_p1_x<rightBottom_p2_x
        && rightBottom_p2_y<leftTop_p1_y&&leftTop_p1_y<leftTop_p2_y) return 1;

    if(leftTop_p2_x<rightBottom_p1_x&&rightBottom_p1_x<rightBottom_p2_x
        && rightBottom_p2_y<rightBottom_p1_y&&rightBottom_p1_y<leftTop_p2_y) return 1;

    if(leftTop_p1_x==leftTop_p2_x&&rightBottom_p1_x==rightBottom_p2_x)
    {
        if(rightBottom_p1_y<leftTop_p2_y&&leftTop_p2_y<leftTop_p1_y) return 1;
        if(rightBottom_p1_y<rightBottom_p2_y&&rightBottom_p2_y<leftTop_p1_y) return 1;

        if(rightBottom_p2_y<leftTop_p1_y&&leftTop_p1_y<leftTop_p2_y) return 1;
        if(rightBottom_p2_y<rightBottom_p1_y&&rightBottom_p1_y<leftTop_p2_y) return 1;
    }

    if(leftTop_p1_y==leftTop_p2_y&&rightBottom_p1_y==rightBottom_p2_y)
    {
        if(leftTop_p1_x<leftTop_p2_x&&leftTop_p2_x<rightBottom_p1_x) return 1;
        if(leftTop_p1_x<rightBottom_p2_x&&rightBottom_p2_x<rightBottom_p1_x) return 1;

        if(leftTop_p2_x<leftTop_p1_x&&leftTop_p1_x<rightBottom_p2_x) return 1;
        if(leftTop_p2_x<rightBottom_p1_x&&rightBottom_p1_x<rightBottom_p2_x) return 1;
    }

    if(leftTop_p1_x==leftTop_p2_x&&rightBottom_p1_x==rightBottom_p2_x)
        if(leftTop_p1_y==leftTop_p2_y&&rightBottom_p1_y==rightBottom_p2_y)
            return 1;

    return 0;
}

int main()
{
    int T;
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d",&N);
        for(int i=0;i<N;i++) scanf("%lf%lf",&p[i].x,&p[i].y);

        left=0;right=50000;
        while(left<=right)
        {
            mid=(left+right)/2;
            init();
            for(int i=0;i<N;i++)
            {
                for(int j=i+1;j<N;j++)
                {
                    if(F(i,j,0,0)) {addEdge(2*i,2*j+1);addEdge(2*j,2*i+1);}
                    if(F(i,j,0,1)) {addEdge(2*i,2*j);addEdge(2*j+1,2*i+1);}
                    if(F(i,j,1,0)) {addEdge(2*i+1,2*j+1);addEdge(2*j,2*i);}
                    if(F(i,j,1,1)) {addEdge(2*i+1,2*j);addEdge(2*j+1,2*i);}
                }
            }
            if(judge()) {ans=mid;left=mid+1;}
            else right=mid-1;
        }
        printf("%d\n",ans);
    }
    return 0;
}