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  • Codeforce 475 C. Kamal-ol-molk's Painting


    从最左上的点開始枚举长宽....

    C. Kamal-ol-molk's Painting
    time limit per test
    2 seconds
    memory limit per test
    256 megabytes
    input
    standard input
    output
    standard output

    Rumors say that one of Kamal-ol-molk's paintings has been altered. A rectangular brush has been moved right and down on the painting.

    Consider the painting as a n × m rectangular grid. At the beginning an x × y rectangular brush is placed somewhere in the frame, with edges parallel to the frame, (1 ≤ x ≤ n, 1 ≤ y ≤ m). Then the brush is moved several times. Each time the brush is moved one unit right or down. The brush has been strictly inside the frame during the painting. The brush alters every cell it has covered at some moment.

    You have found one of the old Kamal-ol-molk's paintings. You want to know if it's possible that it has been altered in described manner. If yes, you also want to know minimum possible area of the brush.

    Input

    The first line of input contains two integers n and m, (1 ≤ n, m ≤ 1000), denoting the height and width of the painting.

    The next n lines contain the painting. Each line has m characters. Character 'X' denotes an altered cell, otherwise it's showed by '.'. There will be at least one altered cell in the painting.

    Output

    Print the minimum area of the brush in a line, if the painting is possibly altered, otherwise print  - 1.

    Sample test(s)
    input
    4 4
    XX..
    XX..
    XXXX
    XXXX
    
    output
    4
    
    input
    4 4
    ....
    .XXX
    .XXX
    ....
    
    output
    2
    
    input
    4 5
    XXXX.
    XXXX.
    .XX..
    .XX..
    
    output
    -1


    #include <iostream>
    #include <cstring>
    #include <cstdio>
    #include <algorithm>
    
    using namespace std;
    
    const int maxn=1100;
    const int INF=0x3f3f3f3f;
    
    char mp[maxn][maxn];
    int n,m,sum[maxn][maxn];
    int ans=INF;
    
    int area(int x1,int y1,int x2,int y2)
    {
    	return sum[x2][y2]-sum[x2][y1-1]-sum[x1-1][y2]+sum[x1-1][y1-1];
    }
    
    int dfs(int x,int y,int wx,int wy)
    {
    	if(area(x,y+1,x+wx-1,y+wy)==wx*wy) return wx+dfs(x,y+1,wx,wy);
    	if(area(x+1,y,x+wx,y+wy-1)==wx*wy) return wy+dfs(x+1,y,wx,wy);
    	return wx*wy;	
    }
    
    int main()
    {
    	scanf("%d%d",&n,&m);
    	for(int i=1;i<=n;i++) scanf("%s",mp[i]+1);
    	bool flag=false;
    	int px=-1,py=-1;
    	for(int i=1;i<=n;i++)
    	{
    		for(int j=1;j<=m;j++)
    		{
    			int t=0;
    			if(mp[i][j]=='X')
    			{
    				if(flag==false)
    				{
    					flag=true; px=i; py=j;
    				}
    				t=1;
    			}	
    			sum[i][j]=sum[i-1][j]+sum[i][j-1]-sum[i-1][j-1]+t;
    		}
    	}
    	
    	int temp=py;
    	for(;temp<=m;temp++) if(mp[px][temp]!='X') break;
    	int leny=temp-py;
    	int lenx;
    	for(int i=px;i<=n;i++)
    	{
    		if(mp[i][py]!='X') break;
    		lenx=i-px+1;
    		if(dfs(px,py,lenx,leny)==sum[n][m])
    		{
    			ans=min(ans,lenx*leny);
    		}
    	}
    	temp=px;
    	for(;temp<=n;temp++) if(mp[temp][py]!='X') break;
    	lenx=temp-px;
    	for(int i=py;i<=m;i++)
    	{
    		if(mp[px][i]!='X') break;
    		leny=i-py+1;
    		if(dfs(px,py,lenx,leny)==sum[n][m])
    		{
    			ans=min(ans,lenx*leny);
    		}
    	}
    
    	if(ans==INF) ans=-1;
    	printf("%d
    ",ans);
    	return 0;
    }
    


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  • 原文地址:https://www.cnblogs.com/jzssuanfa/p/6718556.html
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