C++博客-Dreams-随笔分类-BFS

hdu 1429 胜利大逃亡(续)

DreamSky — Sat, 02 May 2009 00:43:00 GMT

摘要: http://acm.hdu.edu.cn/showproblem.php?pid=1429 //1329152 2009-05-02 08:34:49 Accepted 1429 687MS 4252K 2405 B C++ no way #include阅读全文

DreamSky 2009-05-02 08:43 发表评论

hdu 1728 逃离迷宫

DreamSky — Thu, 23 Apr 2009 11:25:00 GMT

http://acm.hdu.edu.cn/showproblem.php?pid=1728

//1302018 2009-04-23 19:16:46 Accepted 1728 31MS 332K 1788 B C++ no way
#include<iostream>
#include<queue>
#include<stdio.h>
using namespace std;
struct Node
{
    int x;
    int y;
};
int dir[4][2]={{-1,0},{1,0},{0,-1},{0,1}};
char map[102][102];
int m,n,step;
int ok,sx,sy,ex,ey;
int mark[102][102];
void Init()
{
    int i,j;
    cin>>m>>n;
    for(i=0;i<m;i++)
        for(j=0;j<n;j++)
                mark[i][j] = -1;
    for(i=0;i<m;i++)
        scanf("%s",map[i]);
    scanf("%d%d%d%d%d",&step,&sy,&sx,&ey,&ex);
    sx --;
    sy --;
    ex --;
    ey --;
}

void bfs()
{
    int k,turns;
    Node q,p;
    queue<Node>Q;
    p.x = sx;
    p.y = sy;
    Q.push(p);
    while(!Q.empty())
    {
        q = Q.front();
        Q.pop();
        turns = mark[q.x][q.y] + 1;
        for(k=0;k<4;k++)//四方向，每个方向都走到底
        {
            p.x = q.x+dir[k][0];
              p.y = q.y+dir[k][1];
            while(p.x>=0 && p.x<m && p.y>=0 && p.y<n && map[p.x][p.y] == '.')//
            {
                if(mark[p.x][p.y] == -1)
                {
                    if(p.x == ex && p.y== ey && turns <= step )
                    {//最先搜到的就是最优的，
                           ok = 1;
                        return ;
                    }
                    mark[p.x][p.y] = turns;
                    Q.push(p);
                }
                p.x += dir[k][0];
                p.y += dir[k][1];
            }
        }//for(k=0;k<4;k++)
    }//while(!Q.empty())
}

int main()
{
    int t;
    cin>>t;
    while(t--)
    {
        Init();
        if(sx==ex&&sy==ey)
        {
            printf("yes\n");
            continue;
        }
        ok = 0;
        bfs();
        if( ok == 1)
            cout<<"yes"<<endl;
        else
            cout<<"no"<<endl;
    }
    return 0;
}

DreamSky 2009-04-23 19:25 发表评论

zju 2849 Attack of Panda Virus

DreamSky — Fri, 17 Apr 2009 01:15:00 GMT

http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemId=1849

//1833420 2009-04-14 16:41:33 Memory Limit Exceeded  2849 C++ 0 32769 aslys
//1835799 2009-04-17 09:10:34 Accepted  2849 C++ 780 8292 aslys
#include<iostream>
#include<queue>
using namespace std;
struct Node
{
    int vi;
    int vj;
    int day;
    int type;
    friend bool operator < (Node a,Node b)
    {
        if(a.day != b.day)
            return a.day > b.day;
        else
            return a.type > b.type;
    }
};
priority_queue<Node>Q;
int dir[4][2] = {-1,0,1,0,0,-1,0,1};
int m,n;
int gra[501][501];
int sum[250002];
void init()
{
    int i,j;
    Node p;
    memset(sum,0,sizeof(sum));
    //一定要全部清空，切记切记
    for(i=1;i<=m;i++)
    {
        for(j=1;j<=n;j++)
        {
            scanf("%d",&gra[i][j]);
            if(gra[i][j] > 0)
            {
                p.vi = i;
                p.vj = j;
                p.day = 1;
                p.type = gra[i][j];
                Q.push(p);
                sum[gra[i][j]] ++;
            }
        }
    }
}

void bfs()
{
    int k,dmax;
    Node p,q;
    while(!Q.empty())
    {
        q = Q.top();
        Q.pop();
        dmax = -111111111;
        for(k=0;k<4;k++)
        {
            p.vi = q.vi + dir[k][0];
            p.vj = q.vj + dir[k][1];
            if(p.vi>=1 && p.vi<=m && q.vi>=1 && q.vj<=n )
            {
                if(gra[p.vi][p.vj] < 0 )
                {
                    if( gra[p.vi][p.vj] + q.day >= 0)
                    {
                        p.type = q.type;
                        p.day = q.day;
                        gra[p.vi][p.vj] = p.type;
                        Q.push(p);
                        sum[p.type] ++;
                    }
                    else if(gra[p.vi][p.vj] > dmax)//寻找其周围最快传染的机子~
                    {
                        dmax = gra[p.vi][p.vj] ;
                    }
                }
            }//for(k=0;k<4;k++)
        }
        if(dmax != -111111111)
        {
            q.day = dmax * (-1);
            Q.push(q);
        }
    }//while(!Q.empty())
}

int main()
{
    int a,T;
    while(cin>>m>>n)
    {
        init();
        bfs();
        cin>>T;
        while(T--)
        {
            scanf("%d",&a);
            printf("%d\n",sum[a]);
        }
    }
    return 0;
}

DreamSky 2009-04-17 09:15 发表评论

hdu 1026 Ignatius and the Princess I

DreamSky — Wed, 15 Apr 2009 23:58:00 GMT

摘要: http://acm.hdu.edu.cn/showproblem.php?pid=1026 #include#include #include#includeusing namespace std;const int MAX&nb... 阅读全文

DreamSky 2009-04-16 07:58 发表评论

hdu 1239 Calling Extraterrestrial Intelligence Again

DreamSky — Sat, 11 Apr 2009 11:44:00 GMT

http://acm.hdu.edu.cn/showproblem.php?pid=1239

#include<iostream>
#include<cmath>
using namespace std;
int prim[1230];//10000以内的素数共1229个
int main()
{
    int i,j,k;//k记录10000以内素数的个数
    bool primes[10000];
    primes[1] = 0;
    for(i=2;i<=10000;i++)
        primes[i] = 1;
    for(i=2;i<=5000;i++)
    {
        if(primes[i] == 1)
        {
            for(j=2;j*i<=10000;j++)
                primes[j*i] = 0;
        }
    }
    for(i=1,k=0;i<=10000;i++)
        if( primes[i] == 1)
            prim[k++] = i;
    int m,p,q,maxs,id,jd;
    while(cin>>m>>p>>q && m+p+q)
    {
        maxs = 1;
        for(i=k-1;i>=0;i--)//素数值越来越小
        {
            for(j=i ; j<k; j++)//素数值越来越大
            {
                if(prim[i] * prim[j] > m || (double)prim[i]/prim[j] < (double)p/q )
                    break;
                if(maxs < prim[i] * prim[j])
                {
                    maxs = prim[i] * prim[j];
                    id = i;
                    jd = j;
                }
            }
        }
        cout<<prim[id]<<" "<<prim[jd]<<endl;
    }
    return 0;
}

DreamSky 2009-04-11 19:44 发表评论

hdu 1072 Nightmare

DreamSky — Sat, 11 Apr 2009 11:15:00 GMT

http://acm.hdu.edu.cn/showproblem.php?pid=1072

#include<iostream>
#include<queue>
using namespace std;
struct Node
{
    int vi,vj;
    int time;//剩余时间
    int step;//花费时间
};
int gra[9][9];
int mark[9][9];//走到i、j所剩余的时间
int m,n,mins;
int si,sj,ei,ej;
int dir[4][2]={-1,0,1,0,0,-1,0,1};

void bfs()
{
    int k;
    Node p,q;
    queue<Node>Q;
    p.step = 0;
    p.time = 6;
    p.vi = si;
    p.vj = sj;
    Q.push(p);
    mark[si][sj] = p.time;
    while(!Q.empty())
    {
        q = Q.front();
        Q.pop();
        if(q.vi == ei && q.vj == ej)
        {
            if(q.time > 0 )
            {//跑掉
                mins = q.step;
                return ;
            }
            else
                continue;
        }
        if(gra[q.vi][q.vj] == 4) //时间重置
        {
            mark[q.vi][q.vj] = 6;
            q.time = 6;
        }
        for(k=0;k<4;k++)
        {
            p.vi = q.vi + dir[k][0];
               p.vj = q.vj + dir[k][1];
            p.time = q.time - 1;
            p.step = q.step + 1;
            if(p.vi>=0 && p.vi<m && p.vj>=0 && p.vj<n && gra[p.vi][p.vj]!=0 && q.time > 0
                && mark[p.vi][p.vj] < p.time)//不超界又不是墙
            {
                mark[p.vi][p.vj] = p.time;
                Q.push(p);
            }
        }//for(k=0;k<4;k++)
    }//while(!Q.empty())
}
int main()
{
    int t;
    cin>>t;
    while(t--)
    {
        cin>>m>>n;
        int i,j;
        for(i=0;i<m;i++)
        {
            for(j=0;j<n;j++)
            {
                cin>>gra[i][j];
                if(gra[i][j] == 2)//起点
                {
                    si = i;
                    sj = j;
                }
                else if(gra[i][j] == 3)//终点
                {
                    ei = i;
                    ej = j;
                }
                mark[i][j] = 0;
            }
        }

        mins = 1000;
        bfs();
        if(mins != 1000) //逃掉
            cout<<mins<<endl;
        else
            cout<<-1<<endl;
    }
    return 0;
}

DreamSky 2009-04-11 19:15 发表评论

hdu 1195 Open the Lock

DreamSky — Wed, 08 Apr 2009 02:04:00 GMT

摘要: http://acm.hdu.edu.cn/showproblem.php?pid=1195 #include#includeusing namespace std;struct Node{ char data[5]; ... 阅读全文

DreamSky 2009-04-08 10:04 发表评论

zju 1047 Image Perimeters

DreamSky — Wed, 01 Apr 2009 13:31:00 GMT

http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemId=47

#include<iostream>
#include<queue>
#include<string>
using namespace std;
struct Node
{
    int vi;
    int vj;
};
string str[21];
bool mark[21][21];
int m,n,si,sj,sum;
int dir[8][2]={{-1,0},{1,0},{0,-1},{0,1},{-1,-1},{1,-1},{-1,1},{1,1}};
//八个方向
void bfs()
{
    int k;
    Node p,q;
    queue<Node>Q;
    p.vi=si;
    p.vj=sj;
    mark[si][sj]=1;
    Q.push(p);
    while(!Q.empty())
    {
        q=Q.front();
        Q.pop();
        for(k=0;k<4;k++)//上、下、左、右
        {
            p.vi=q.vi+dir[k][0];
            p.vj=q.vj+dir[k][1];
            if(p.vi>=0 && p.vi<m && p.vj>=0 && p.vj<n)
            {
                if(str[p.vi][p.vj]=='.')
                    sum++;
                else if(str[p.vi][p.vj]=='X' && mark[p.vi][p.vj]==0)
                {
                    mark[p.vi][p.vj]=1;
                    Q.push(p);
                }
            }
            else
                sum++;
        }
        for(k=4;k<8;k++)//左上、左下、右上、右下
        {
            p.vi=q.vi+dir[k][0];
            p.vj=q.vj+dir[k][1];
            if(p.vi>=0 && p.vi<m && p.vj>=0 && p.vj<n)
            {
                if(str[p.vi][p.vj]=='X' && mark[p.vi][p.vj]==0)
                {
                    mark[p.vi][p.vj]=1;
                    Q.push(p);
                }
            }
        }
    }//while(!Q.empty())
}

int main()
{
    while(cin>>m>>n>>si>>sj && m+n+si+sj)
    {
        si--;
        sj--;
        int i,j;
        for(i=0;i<m;i++)
            cin>>str[i];
        sum=0;
        memset(mark,0,sizeof(mark));
        bfs();
        cout<<sum<<endl;
    }
    return 0;
}

DreamSky 2009-04-01 21:31 发表评论