以最少的步数绘制立方体顶点 [英] Draw cube vertices with fewest number of steps
问题描述
如何绘制所有立方体的顶点所需的最少步数是多少? /i.stack.imgur.com/9Aq87.gifalt =显示立方体坐标的图表>
到目前为止,我已将其缩小到16个步骤:
0,0,0
0,0,1
0,1,1
1, 1,1
1,1,0
0,1,0
0,0,0
1,0,0
1,0,1
0,0,1
0,1,1
0,1,0
1,1,0
1,0,0
1,0,0 ,1
1,1,1
我认为它可以减少少于16步因为只有12个顶点需要绘制
你可以在这里查看一个可以在three.js javascript中使用的示例:
http://jsfiddle.net/kmturley/5aeucehf/show/
我为这个
首先是立方体表示:
// ---- -------------------------------------------------- ---------------------
#define a 0.5
double pnt [] =
{
-a, -a,-a,//指向0
-a,-a,+ a,
-a,+ a,-a,
-a,+ a,+ a,
+ a,-a,-a,
+ a,-a,+ a,
+ a,+ a,-a,
+ a,+ a,+ a ,//指向7
1e101,1e101,1e101,//结束标记
};
#undef a
int lin [] =
{
0,1,
0,2,
0,4,
1 ,3,
1,5,
2,3,
2,6,
3,7,
4,5,
4,6 ,
5,7,
6,7,
-1,-1,//结束标记
};
// int solution [] = {0,1,3,1,5,4,0,2,3,7,5,4,6,2,6,7,-1}; //找到折线解决方案
// --------------------------------------- ------------------------------------
void draw_lin(double * pnt,int * lin )
{
glBegin(GL_LINES);
for(int i = 0; lin [i]> = 0;)
{
glVertex3dv(pnt +(lin [i] * 3));我++;
glVertex3dv(pnt +(lin [i] * 3));我++;
}
glEnd();
}
// --------------------------------------- ------------------------------------
void draw_pol(double * pnt,int * pol )
{
glBegin(GL_LINE_STRIP);
for(int i = 0; pol [i]> = 0; i ++)glVertex3dv(pnt +(pol [i] * 3));
glEnd();
}
// --------------------------------------- ------------------------------------
$ b $现在是求解器:$ $ p $
// ----- -------------------------------------------------- --------------------
struct _vtx // vertex
{
List< int>一世; //连接到(顶点...)
_vtx(){}; _vtx(_vtx& a){* this = a; }; 〜_vtx(){}; _vtx * operator =(const _vtx * a){* this = * a;返回这个; }; / * _ vtx * operator =(const _vtx& a){... copy ... return this; }; * /
};
const int _max = 16; //知道解决方案的大小(不用费时寻找更长的解决方案)
int use [_max],uses = 0; //临时行使用标志
int pol [_max],pols = 0; // temp解决方案
int sol [_max + 2],sols = 0; //最好找到解决方案
List< _vtx> VTX; //模型顶点+连接信息
// ------------------------------------- --------------------------------------
void _solve(int a)
{
_vtx * v; int i,j,k,l,a0,a1,b0,b1;
//添加点到实际折线
pol [pols] = a;政客++; V =&安培; VTX [A];
//测试解
for(l = 0,i = 0; i< uses; i ++)use [i] = 0; (a0 = pol [0],a1 = pol [1],i = 1; i 为(j = 0) ,k = 0; k <使用; k ++)
{
b0 = lin [j]; J ++;
b1 = lin [j]; J ++; ((a0 == b0)&&(a1 == b1))||((a0 == b1)&&(a1 == b0)
if(!use [k])if ))){use [k] = 1;升++; }
}
if(l == uses)//找到更好的解法
if((pols (sols = 0; sols pols; sols ++)sol [sols] = pol [sols];
//仅当pol不太大时递归
if(pols + 1 i.num; i ++)_solve(v-> i .DAT [I]);
//返回到之前的状态
pols--; POL [政客] = - 1;
}
// --------------------------------------- ------------------------------------
void solve(double * pnt,int * lin )
{
int i,j,a0,a1;
//初始化大小
for(i = 0; i <_max; i ++){use [i] = 0; POL [I] = - 1;溶胶[I] = - 1; (i = 0,j = 0; pnt [i] <1e100; i + = 3,j ++);}
; vtx.allocate(J); vtx.num = j的;
for(i = 0; i //初始化连接
for(uses = 0,i = 0; lin [i]> = 0; uses ++)
{
a0 = lin [i]我++;
a1 = lin [i];我++;
vtx [a0] .i.add(a1);
vtx [a1] .i.add(a0);
}
//开始真正的解决方案(无论哪个顶点在立方体上都是第一个)
pols = 0;溶胶= _MAX + 1; _solve(0);
sol [sols] = - 1;如果(sol [0] <0)sols = 0;
}
// --------------------------------------- ------------------------------------
用法:
solve(pnt,lin); //调用一次来计算解决方案
glColor3f(0.2,0.2,0.2); draw_lin(PNT,林); //绘制灰色轮廓
glColor3f(1.0,1.0,1.0); draw_pol(PNT,溶胶); //通过解决方案覆盖以直观检查正确性(Z缓冲区也必须以相同的值传递!!!)
列表
- 只是我的动态数组模板
-
List< ; INT> x
相当于int x []
-
x.add(5 )
...将5添加到列表的最后 -
x.num
列表中的条目 -
x.allocate(100)
将列表大小预先分配到100个条目(以避免重定位速度变慢) b
$ b解决(pnt,lin)算法
-
首先准备顶点数据
- 每个顶点
vtx [i]
对应于点i-第一点在pnt
表中 - i [] list包含连接到这个顶点的每个顶点的索引
-
以顶点0开始(在立方体上与开始点无关)
- 否则会有循环遍历每个顶点作为开始点
-
_solve(a)
- 它为顶点索引添加实际解决方案
pol [pols]
- 然后测试实际sol中有多少行如果所有来自lin []的行都被绘制出来,并且解决方案比已经找到的小
- ,则将其复制为新解决方案
- 如果实际解决方案不是太长,递归地添加下一个顶点
- 作为连接到上一个顶点的顶点之一
- 限制组合数目
- 它为顶点索引添加实际解决方案
-
结束sol [sols]保存解决方案顶点索引列表
- sols是所使用顶点的数量(第1行)
- 每个顶点
[注意]
- 代码不是很干净,它工作(对不起)
- 希望我没有忘记复制一些东西
What's the fewest number of steps needed to draw all of the cube's vertices, without picking up the pen from the paper?
So far I have reduced it to 16 steps:
0, 0, 0 0, 0, 1 0, 1, 1 1, 1, 1 1, 1, 0 0, 1, 0 0, 0, 0 1, 0, 0 1, 0, 1 0, 0, 1 0, 1, 1 0, 1, 0 1, 1, 0 1, 0, 0 1, 0, 1 1, 1, 1
I presume it can be reduced less than 16 steps as there are only 12 vertices to be drawn
You can view a working example in three.js javascript here: http://jsfiddle.net/kmturley/5aeucehf/show/
解决方案Well I encoded a small brute force solver for this
- the best solution is with 16 vertexes
- took about 11.6 sec to compute
- all is in C++ (visualization by OpenGL)
First the cube representation:
//--------------------------------------------------------------------------- #define a 0.5 double pnt[]= { -a,-a,-a, // point 0 -a,-a,+a, -a,+a,-a, -a,+a,+a, +a,-a,-a, +a,-a,+a, +a,+a,-a, +a,+a,+a, // point 7 1e101,1e101,1e101, // end tag }; #undef a int lin[]= { 0,1, 0,2, 0,4, 1,3, 1,5, 2,3, 2,6, 3,7, 4,5, 4,6, 5,7, 6,7, -1,-1, // end tag }; // int solution[]={ 0, 1, 3, 1, 5, 4, 0, 2, 3, 7, 5, 4, 6, 2, 6, 7, -1 }; // found polyline solution //--------------------------------------------------------------------------- void draw_lin(double *pnt,int *lin) { glBegin(GL_LINES); for (int i=0;lin[i]>=0;) { glVertex3dv(pnt+(lin[i]*3)); i++; glVertex3dv(pnt+(lin[i]*3)); i++; } glEnd(); } //--------------------------------------------------------------------------- void draw_pol(double *pnt,int *pol) { glBegin(GL_LINE_STRIP); for (int i=0;pol[i]>=0;i++) glVertex3dv(pnt+(pol[i]*3)); glEnd(); } //---------------------------------------------------------------------------
Now the solver:
//--------------------------------------------------------------------------- struct _vtx // vertex { List<int> i; // connected to (vertexes...) _vtx(){}; _vtx(_vtx& a){ *this=a; }; ~_vtx(){}; _vtx* operator = (const _vtx *a) { *this=*a; return this; }; /*_vtx* operator = (const _vtx &a) { ...copy... return this; };*/ }; const int _max=16; // know solution size (do not bother to find longer solutions) int use[_max],uses=0; // temp line usage flag int pol[_max],pols=0; // temp solution int sol[_max+2],sols=0; // best found solution List<_vtx> vtx; // model vertexes + connection info //--------------------------------------------------------------------------- void _solve(int a) { _vtx *v; int i,j,k,l,a0,a1,b0,b1; // add point to actual polyline pol[pols]=a; pols++; v=&vtx[a]; // test for solution for (l=0,i=0;i<uses;i++) use[i]=0; for (a0=pol[0],a1=pol[1],i=1;i<pols;i++,a0=a1,a1=pol[i]) for (j=0,k=0;k<uses;k++) { b0=lin[j]; j++; b1=lin[j]; j++; if (!use[k]) if (((a0==b0)&&(a1==b1))||((a0==b1)&&(a1==b0))) { use[k]=1; l++; } } if (l==uses) // better solution found if ((pols<sols)||(sol[0]==-1)) for (sols=0;sols<pols;sols++) sol[sols]=pol[sols]; // recursion only if pol not too big if (pols+1<sols) for (i=0;i<v->i.num;i++) _solve(v->i.dat[i]); // back to previous state pols--; pol[pols]=-1; } //--------------------------------------------------------------------------- void solve(double *pnt,int *lin) { int i,j,a0,a1; // init sizes for (i=0;i<_max;i++) { use[i]=0; pol[i]=-1; sol[i]=-1; } for(i=0,j=0;pnt[i]<1e100;i+=3,j++); vtx.allocate(j); vtx.num=j; for(i=0;i<vtx.num;i++) vtx[i].i.num=0; // init connections for(uses=0,i=0;lin[i]>=0;uses++) { a0=lin[i]; i++; a1=lin[i]; i++; vtx[a0].i.add(a1); vtx[a1].i.add(a0); } // start actual solution (does not matter which vertex on cube is first) pols=0; sols=_max+1; _solve(0); sol[sols]=-1; if (sol[0]<0) sols=0; } //---------------------------------------------------------------------------
Usage:
solve(pnt,lin); // call once to compute the solution glColor3f(0.2,0.2,0.2); draw_lin(pnt,lin); // draw gray outline glColor3f(1.0,1.0,1.0); draw_pol(pnt,sol); // overwrite by solution to visually check correctness (Z-buffer must pass also on equal values!!!)
List
- is just mine template for dynamic array
List<int> x
is equivalent toint x[]
x.add(5)
... adds 5 to the end of listx.num
is the used size of list in entriesx.allocate(100)
preallocate list size to 100 entries (to avoid relocations slowdowns)
solve(pnt,lin) algorithm
first prepare vertex data
- each vertex
vtx[i]
corresponds to point i-th point inpnt
table - i[] list contains the index of each vertex connected to this vertex
- each vertex
start with vertex 0 (on cube is irrelevant the start point
- otherwise there would be for loop through every vertex as start point
_solve(a)
- it adds a vertex index to actual solution
pol[pols]
- then test how many lines is present in actual solution
- and if all lines from lin[] are drawn and solution is smaller than already found one
- copy it as new solution
- after test if actual solution is not too long recursively add next vertex
- as one of the vertex that is connected to last vertex used
- to limit the number of combinations
- it adds a vertex index to actual solution
at the end sol[sols] hold the solution vertex index list
- sols is the number of vertexes used (lines-1)
[Notes]
- the code is not very clean but it works (sorry for that)
- hope I did not forget to copy something
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