<span style="font-size: 18pt; font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);">K - </span><span style="color: blue; font-size: 18pt; font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);">Quadtrees</span>
Time
Limit:3000MS Memory
Limit:0KB 64bit IO
Format:%lld & %llu
Appoint
description: System Crawler (2014-01-02)
Description
| Quadtrees |
A quadtree is a representation
format used to encode images. The fundamental idea behind the quadtree is that
any image can be split into four quadrants. Each quadrant may again be split in
four sub quadrants, etc. In the quadtree, the image is represented by a parent
node, while the four quadrants are represented by four child nodes, in a
predetermined order.
Of course, if the whole image is
a single color, it can be represented by a quadtree consisting of a single node.
In general, a quadrant needs only to be subdivided if it consists of pixels of
different colors. As a result, the quadtree need not be of uniform depth.
A modern computer artist works
with black-and-white images of 
units, for a total of 1024 pixels per image. One of the
operations he performs is adding two images together, to form a new image. In
the resulting image a pixel is black if it was black in at least one of the
component images, otherwise it is white.
This particular artist believes
in what he calls the preferred fullness: for an image to be
interesting (i.e. to sell for big bucks) the most important property is the
number of filled (black) pixels in the image. So, before adding two images
together, he would like to know how many pixels will be black in the resulting
image. Your job is to write a program that, given the quadtree representation of
two images, calculates the number of pixels that are black in the image, which
is the result of adding the two images together.
In the figure, the first example
is shown (from top to bottom) as image, quadtree, pre-order string (defined
below) and number of pixels. The quadrant numbering is shown at the top of the
figure.
Input Specification
The first line of input
specifies the number of test cases (N) your program has to process.
The input for each test case is
two strings, each string on its own line. The string is the pre-order
representation of a quadtree, in which the letter ‘p‘ indicates a
parent node, the letter ‘f‘ (full) a black quadrant and the letter
‘e‘ (empty) a white quadrant. It is guaranteed that each string
represents a valid quadtree, while the depth of the tree is not more than 5
(because each pixel has only one color).
Output Specification
For each test case, print on one
line the text ‘There are X black pixels.‘,
where X is the number of black pixels in the resulting
image.
Example Input
3
ppeeefpffeefe
pefepeefe
peeef
peefe
peeef
peepefefe
Example Output
There are 640 black pixels.
There are 512 black pixels.
There are 384 black pixels.
题意：有一个用四叉树表示的图，该图用P，E，F来表示，P表示父节点，F表示黑色，E表示白色，整个图的大小为1024。每个子图都能分成四个部分（当颜色不同的时候才须要划分），如今要把两个图合并成一个图，求合并后图有多少黑色像素。
#include<stdio.h>
#include<cstring>
#include<algorithm>
int T;
char s1[2049],s2[2049];
struct quadtree
{
int num;
quadtree *next[4];
quadtree()
{
num=0;
for(int i=0; i<4; i++)next[i]=0;
}
};
quadtree *build(char *s)///建树
{
quadtree *now=new quadtree;
int len=strlen(s);
if(s[0]!=‘p‘)
{
now->num=1;
if(s[0]!=‘f‘)
{
delete now;
now=NULL;
}
return now;
}
int up=4;///子树数目
int d=1;
for(int i=1; d<=up&&i<len; i++)
{
if(s[i]==‘p‘)
{
now->next[d-1]=build(s+i);
int dx=0,dy=4;
while(dx<dy)
{
dx++;
if(s[i+dx]==‘p‘)dy+=4;
}
i+=dx;///i变到下一颗子树的起始位置
}
else
{
now->next[d-1]=build(s+i);
}
d++;
}
return now;
}
quadtree *merge_(quadtree *p,quadtree *q)///合并
{
if(p||q)
{
quadtree *root=new quadtree;
if(p&&q)for(int i=0; i<4; i++)
{
if(p->num||q->num)
{
root->num=1; ///子树已经全为黑色，不须要继续递归
continue;
}
root->next[i]=merge_(p->next[i],q->next[i]);
}
else if(p==NULL&&q)for(int i=0; i<4; i++)
{
if(q->num)
{
root->num=1;; ///子树已经全为黑色，不须要继续递归
continue;
}
root->next[i]=merge_(NULL,q->next[i]);
}
else for(int i=0; i<4; i++)
{
if(p->num)
{
root->num=1;; ///子树已经全为黑色，不须要继续递归
continue;
}
root->next[i]=merge_(p->next[i],NULL);
}
return root;
}
return NULL;
}
int dfs(quadtree *p,int num)
{
if(p==NULL)return 0;
int sum=0;
if(p->num)sum+=num;
for(int i=0; i<4; i++)
{
sum+=dfs(p->next[i],num/4);
}
return sum;
}
int main()
{
//freopen("in.txt","r",stdin);
quadtree *root1,*root2,*root;
scanf("%d",&T);
while(T--)
{
scanf("%s%s",s1,s2);
root=root1=root2=NULL;
root1=build(s1);
root2=build(s2);
root=merge_(root1,root2);
printf("There are %d black pixels.\n",dfs(root,1024));
}
return 0;
}
UVA 297 Quadtrees（四叉树建树、合并与遍历）,布布扣,bubuko.com