poj 1175 starry night#BFS#模拟

最新推荐文章于 2020-06-25 16:17:55 发布

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#struct #output #c #input

本文介绍了一种使用BFS算法处理二维矩阵中的云团，并通过旋转和平面对称操作比较不同云团的方法。针对每个独立的云团，算法将其标准化并映射到固定坐标系中进行比较。

Hint

Just to make it clearer, notice that this sample input corresponds to the following picture of the sky.

Notice that this sample output corresponds to the following picture.

/**
poj 1175 #BFS

BFS出每个云团，问题在于处理两个云团是否相同。
处理方法是将每个云团映射到[0,0] 到[n,m]的矩阵中，然后就可以旋转或对称操作之后来比较了。
*/
#include <stdio.h>
#include <queue>
#include <algorithm>
#include <iostream>
using namespace std;

#define N 555
#define M 111
#define INF 55555
char mat[M][M];
struct Point
{
    int x,y;
    Point(int a = 0,int b = 0)
    {
        x = a;
        y = b;
    }
};
bool cmp(Point a,Point b)
{
    if(a.x == b.x)
        return a.y < b.y;
    return a.x < b.x;
}
struct node
{
    int m,n,x,y;
    vector<Point> vec;
    void draw(char c)
    {
        int len = vec.size();
        for(int i = 0; i < len; ++i)
            mat[x+vec[i].x][y+vec[i].y] = c;
    }

    void push(vector<Point> ve)
    {
        int minx,miny,maxx,maxy;
        minx = miny = INF;
        maxx = maxy = -1;
        int len = ve.size(),i;
        for(i = 0; i < len; ++i)
        {
            minx = min(minx,ve[i].x);
            miny = min(miny,ve[i].y);
            maxx = max(maxx,ve[i].x);
            maxy = max(maxy,ve[i].y);
        }
        n = maxx - minx + 1;
        m = maxy - miny + 1;
        x = minx;
        y = miny;
        for(i = 0; i < len; ++i)
            vec.push_back(Point(ve[i].x-x,ve[i].y-y));
        sort(vec.begin(),vec.end(),cmp);
    }
    void rotate()
    {
        int i,t,len = vec.size();
        for(i = 0; i < len; ++i)
        {
            t = vec[i].y;
            vec[i].y = n - vec[i].x - 1;
            vec[i].x = t;
        }
        swap(m,n);
        sort(vec.begin(),vec.end(),cmp);
    }
    void reservey()
    {
        int i,len = vec.size();
        for(i = 0; i < len; ++i)
        {
            vec[i].x = n - vec[i].x - 1;
        }
        sort(vec.begin(),vec.end(),cmp);
    }
    void reservex()
    {
        int i,len = vec.size();
        for(i = 0; i < len; ++i)
            vec[i].y = m - vec[i].y - 1;
        sort(vec.begin(),vec.end(),cmp);
    }

}c[N];
bool same(node t,node p)
{

    if(t.m == p.m && t.n == p.n && t.vec.size() == p.vec.size())
    {
        int i,len = t.vec.size();
        for(i = 0; i < len && t.vec[i].x == p.vec[i].x && t.vec[i].y == p.vec[i].y; ++i);
        return i == len;
    }
    return 0;
}
bool similars(node t,node p)
{
    node pt;
    if(t.m != p.m & t.n != p.n && t.m != p.n && t.n != p.m)
        return 0;
    for(int i = 0; i < 4; ++i)
    {

        if(same(t,p))
            return 1;
        pt = p;

        pt.reservey();
        if(same(t,pt))
            return 1;

        pt = p;
        pt.reservex();
        if(same(t,pt))
            return 1;

        p.rotate();
    }
    return 0;
}
int move[][2] = {0,1, 1,0, 0,-1, -1,0, 1,-1, 1,1, -1,1, -1,-1};
int n,m;
bool ok(int x,int y)
{
    return x >= 0 && x < n && y >= 0 && y < m && mat[x][y] == '1';
}
vector<Point> bfs(int x,int y)
{
    vector<Point> vv;
    Point p(x,y),pt;
    queue<Point> que;
    int i;
    que.push(p);
    vv.push_back(p);
    mat[x][y] = '0';
    while(!que.empty())
    {
        p = que.front();
        que.pop();
        for(i = 0; i < 8; ++i)
        {
            pt = Point(p.x+move[i][0],p.y+move[i][1]);
            if(ok(pt.x,pt.y))
            {
                que.push(pt);
                vv.push_back(pt);
                mat[pt.x][pt.y] = '0';
            }
        }
    }
    return vv;
}

int vis[N];
int main()
{
    scanf("%d%d",&m,&n);
    int i,j,k = 0;
    for(i = 0; i < n; ++i)
        scanf("%s",mat[i]);
    for(i = 0; i < n; ++i)
        for(j = 0; j < m; ++j)
            if(mat[i][j] =='1')
                c[k++].push(bfs(i,j));
    char ch = 'a';
    for(i = 0; i < k; ++i)
    {
        if(vis[i])
            continue;
        vis[i] = 1;
        c[i].draw(ch);
        for(j = i + 1; j < k; ++j)
            if(!vis[j] && similars(c[i],c[j]))
            {
                c[j].draw(ch);
                vis[j] = 1;
            }
        ++ch;
    }
    for(i = 0; i < n; ++i)
        printf("%s\n",mat[i]);
    return 0;
}