blocks|key|1392210|text|你的向量是空的。所以你不能使用[0][0]。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1392211|下面是如何声明它的：|1392212|a.push_back(vector<point>());
a[0].push_back(p);|code-block|syntax|javascript|1392213|如果您从一开始就知道您将拥有多少项，则可以执行以下操作：|1392214|vector<vector<point>+>+a(10,+vector<point>(10));|1392215|它是一个包含10个向量的向量，其中包含10个点。然后你就可以使用|1392216|a[4][4]+=+p;|1392217|然而，我认为使用向量的向量是令人困惑的。如果需要数组，请考虑使用uBLAS+http://www.boost.org/doc/libs/1_41_0/libs/numeric/ublas/doc/index.htm|1392218|#include+<boost/numeric/ublas/matrix.hpp>
#include+<boost/numeric/ublas/io.hpp>

int+main+()+{
++++using+namespace+boost::numeric::ublas;
++++matrix<double>+m+(3,+3);
++++for+(unsigned+i+=+0;+i+<+m.size1+();+%2B%2B+i)
++++++++for+(unsigned+j+=+0;+j+<+m.size2+();+%2B%2B+j)
++++++++++++m+(i,+j)+=+3+*+i+%2B+j;
++++std::cout+<<+m+<<+std::endl;
}|1392219|entityMap|0|LINK|mutability|MUTABLE|url|http://www.boost.org/doc/libs/1_41_0/libs/numeric/ublas/doc/index.htm^0|F|6|0|0|0|0|0|0|0|12|1X|0|0|0^^$0|@$1|2|3|4|5|6|7|16|8|@$9|17|A|18|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|19|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|1A|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|1B|8|@]|D|@]|E|$]]|$1|O|3|P|5|J|7|1C|8|@]|D|@]|E|$K|L]]|$1|Q|3|R|5|6|7|1D|8|@]|D|@]|E|$]]|$1|S|3|T|5|J|7|1E|8|@]|D|@]|E|$K|L]]|$1|U|3|V|5|6|7|1F|8|@]|D|@$9|1G|A|1H|1|1I]]|E|$]]|$1|W|3|X|5|J|7|1J|8|@]|D|@]|E|$K|L]]|$1|Y|3|-4|5|6|7|1K|8|@]|D|@]|E|$]]]|Z|$10|$5|11|12|13|E|$14|15]]]]

Your vector is empty. So you can't use <code>[0][0]</code>.

Here is how you declare it:

<pre><code>a.push_back(vector&lt;point&gt;());
a[0].push_back(p);
</code></pre>

If you know how many items you will have from the start, you can do :

<pre><code>vector&lt;vector&lt;point&gt; &gt; a(10, vector&lt;point&gt;(10));
</code></pre>

It's a vector containing 10 vectors containing 10 point. Then you can use

<pre><code>a[4][4] = p;
</code></pre>

However, I believe that using vector of vectors is confusing. If you want an array, consider using uBLAS <a href="http://www.boost.org/doc/libs/1_41_0/libs/numeric/ublas/doc/index.htm" rel="noreferrer">http://www.boost.org/doc/libs/1_41_0/libs/numeric/ublas/doc/index.htm</a>

<pre><code>#include &lt;boost/numeric/ublas/matrix.hpp&gt;
#include &lt;boost/numeric/ublas/io.hpp&gt;

int main () {
 using namespace boost::numeric::ublas;
 matrix&lt;double&gt; m (3, 3);
 for (unsigned i = 0; i &lt; m.size1 (); ++ i)
 for (unsigned j = 0; j &lt; m.size2 (); ++ j)
 m (i, j) = 3 * i + j;
 std::cout &lt;&lt; m &lt;&lt; std::endl;
}
</code></pre>

blocks|key|1176847|text|您已经构造了一个空的向量向量，并尝试在不向其添加任何元素的情况下取消引用第一个元素。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1176848|向量不像(某些)关联数组那样工作，在关联数组中，试图访问缺失的值会将其添加到集合中。您需要确保矢量具有适当数量的条目，然后才能尝试使用适当形式的矢量构造函数或使用push_back来访问它们。|1176849|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

You have constructed a vector of vectors that is empty, and have tried to dereference the first element without adding any elements to it.

Vectors don't work like (some) associative arrays, where attempting to access a value that's missing will add it to the collection. You need to ensure the vectors have an appropriate number of entries before you try to access them by using the appropriate form of the vector constructor or by using push_back.

blocks|key|1392350|text|这是另一个建议。您要完成的任务以前已经完成，可以在Boost+Multi-Array中找到。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1392351|entityMap|0|LINK|mutability|MUTABLE|url|http://www.boost.org/doc/libs/1_41_0/libs/multi_array/doc/index.html^0|P|H|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

Here's another suggestion. What you're trying to accomplish has been done before and can be found within the <a href="http://www.boost.org/doc/libs/1_41_0/libs/multi_array/doc/index.html" rel="noreferrer">Boost Multi-Array</a>.

blocks|key|1176900|text|您可以定义vectorMatrix，它是一个向量矩阵，如下所示。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1176901|类：|1176902|class+vectorMatrix
{
++std::vector<object>+**cell;

++int+columns;
++int+rows;

++public:
++vectorMatrix(int+columns,+int+rows);
++virtual+~vectorMatrix();

++void+addCellAt(int+row,+int+column,+const+object&+entry);

++virtual+std::vector<object>*+getCell(int+row,+int+column);

++void+clearMatrix();
};|code-block|syntax|javascript|1176903|定义构造函数：|1176904|vectorMatrix::vectorMatrix(int+columns,+int+rows)
{
+++this->columns+=+columns;
+++this->rows+=+rows;

+++cell+=+new+std::vector<object>*+[columns];

+++for+(int+i+=+0;+i+<+columns;+i%2B%2B)
+++{
+++++++cell[i]+=+new+std::vector<object>[rows];
+++}
}|1176905|一种添加条目的方法：|1176906|void+vectorMatrix::addCellAt(int+row,+int+column,+const+object&+entry)
{
+++++++cell[channel][timeSlot].push_back(entry);
}|1176907|获取指向给定行和列中的向量的指针：|1176908|std::vector<object>*+vectorMatrix::getCell(int+row,+int+column)
{
++++return+&cell[row][column];
}|1176909|清除所有矩阵：|1176910|void+vectorMatrix::clearMatrix()
{
++++for+(int+tmpRow+=+0;+tmpRow+<+columns;+tmpRow+%2B%2B)
++++{
++++++++for(int+tmpColumn+=+0;+tmpColumn+<+rows;+tmpColumn+%2B%2B)
++++++++{
++++++++++++cell[tmpRow][tmpColumn].clear();
++++++++}
++++}
}|1176911|entityMap^0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|11|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|12|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|13|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|14|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|15|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|16|8|@]|9|@]|A|$G|H]]|$1|Q|3|R|5|6|7|17|8|@]|9|@]|A|$]]|$1|S|3|T|5|F|7|18|8|@]|9|@]|A|$G|H]]|$1|U|3|V|5|6|7|19|8|@]|9|@]|A|$]]|$1|W|3|X|5|F|7|1A|8|@]|9|@]|A|$G|H]]|$1|Y|3|-4|5|6|7|1B|8|@]|9|@]|A|$]]]|Z|$]]

You can define vectorMatrix[][], which is a matrix of vectors as follows.

Class:

<pre><code>class vectorMatrix
{
 std::vector&lt;object&gt; **cell;

 int columns;
 int rows;

 public:
 vectorMatrix(int columns, int rows);
 virtual ~vectorMatrix();

 void addCellAt(int row, int column, const object&amp; entry);

 virtual std::vector&lt;object&gt;* getCell(int row, int column);

 void clearMatrix();
};
</code></pre>

Define constructor:

<pre><code>vectorMatrix::vectorMatrix(int columns, int rows)
{
 this-&gt;columns = columns;
 this-&gt;rows = rows;

 cell = new std::vector&lt;object&gt;* [columns];

 for (int i = 0; i &lt; columns; i++)
 {
 cell[i] = new std::vector&lt;object&gt;[rows];
 }
}
</code></pre>

A method for adding an entry:

<pre><code>void vectorMatrix::addCellAt(int row, int column, const object&amp; entry)
{
 cell[channel][timeSlot].push_back(entry);
}
</code></pre>

Getting a pointer to the vector in a given row and column:

<pre><code>std::vector&lt;object&gt;* vectorMatrix::getCell(int row, int column)
{
 return &amp;cell[row][column];
}
</code></pre>

Clearing all the matrix:

<pre><code>void vectorMatrix::clearMatrix()
{
 for (int tmpRow = 0; tmpRow &lt; columns; tmpRow ++)
 {
 for(int tmpColumn = 0; tmpColumn &lt; rows; tmpColumn ++)
 {
 cell[tmpRow][tmpColumn].clear();
 }
 }
}
</code></pre>

blocks|key|1392466|text|设法让它工作起来了。我从其他地方学到了'typedef‘的概念。尝试下面的代码，它可以工作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1392467|#include+<iostream>
#include+<stdlib.h>
#include+<stdio.h>
#include+<vector>


using+namespace+std;

int+main()
{
++++int+i+=+0;
++++int+j+=+0;

///////////////////////////////////////////////////////////

++++typedef+vector<string>+vecRow;
++++typedef+vector<vecRow>+vecCol;

++++vecRow+vr;
++++vecCol+vc;
///////////////////////////////////////////////////////////
//+Assigning+string+elements+to+the+2d+array

++++for(i=0;i<10;i%2B%2B)
++++{
++++++++++++for(j=0;j<5;j%2B%2B)
++++++++++++{
++++++++++++++++vr.push_back("string+["%2Bto_string(i)%2B"]["%2Bto_string(j)%2B"]");
++++++++++++}
++++++++++++vecRow+vr_temp+=+vecRow(vr);
++++++++++++vc.push_back(vr_temp);
++++++++++++vr.clear();
++++}

///////////////////////////////////////////////////////////
//+Printing+back+the+elements+from+the+2D+array

++++for(auto+element+:+vc)
++++{
++++++++++++for(unsigned+int+ictr+=+0;ictr+<+element.size()+;+ictr%2B%2B)
++++++++++++{
++++++++++++++++cout<<element[ictr]<<"\t";
++++++++++++}
++++++++++++cout<<endl;
++++}

++++getchar();
++++return+0;
}|code-block|syntax|javascript|1392468|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Managed to get it working. Picked up the idea for the 'typedef' from somewhere else. Try the below code, it works:

<pre><code>#include &lt;iostream&gt;
#include &lt;stdlib.h&gt;
#include &lt;stdio.h&gt;
#include &lt;vector&gt;


using namespace std;

int main()
{
 int i = 0;
 int j = 0;

///////////////////////////////////////////////////////////

 typedef vector&lt;string&gt; vecRow;
 typedef vector&lt;vecRow&gt; vecCol;

 vecRow vr;
 vecCol vc;
///////////////////////////////////////////////////////////
// Assigning string elements to the 2d array

 for(i=0;i&lt;10;i++)
 {
 for(j=0;j&lt;5;j++)
 {
 vr.push_back("string ["+to_string(i)+"]["+to_string(j)+"]");
 }
 vecRow vr_temp = vecRow(vr);
 vc.push_back(vr_temp);
 vr.clear();
 }

///////////////////////////////////////////////////////////
// Printing back the elements from the 2D array

 for(auto element : vc)
 {
 for(unsigned int ictr = 0;ictr &lt; element.size() ; ictr++)
 {
 cout&lt;&lt;element[ictr]&lt;&lt;"\t";
 }
 cout&lt;&lt;endl;
 }

 getchar();
 return 0;
}
</code></pre>

blocks|key|1392509|text|您可以使用resize()；例如，这里我将a的大小调整为100+x+200的数组：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1392510|++vector<vector<point>+>+a;+//+2D+array+++++++++++++++++++++++++++++++++++++++++
++a.resize(100);
++for_each(a.begin(),a.end(),[](vector<point>&+v){v.resize(200);});
++point+p(2,3);
++a[0][0]+=+p;+//+ok+now++++++++++++++++++++++++++++++++++++++++++++++++++++|code-block|syntax|javascript|1392511|entityMap^0|5|8|L|1|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

You can use <code>resize()</code>; e.g., here I resize <code>a</code> to a 100 x 200 array:

<pre><code> vector&lt;vector&lt;point&gt; &gt; a; // 2D array 
 a.resize(100);
 for_each(a.begin(),a.end(),[](vector&lt;point&gt;&amp; v){v.resize(200);});
 point p(2,3);
 a[0][0] = p; // ok now 
</code></pre>

blocks|key|1177038|text|最简单的方法是使用resize()方法，如下所示：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1177039|vector+<vector<int>>+v;
cin>>n>>m;+//n+is+rows+and+m+is+columns
v.resize(n,vector<int>(m));
for(i=0;i<n;i%2B%2B)++++++//+inserts+elements+into+the+vector+v
+for(j=0;j<m;j%2B%2B)
++cin>>v[i][j];+

for(i=0;i<n;i%2B%2B)++++++//accesses+elements+of+vector+v
+for(j=0;j<m;j%2B%2B)
+++cout<<v[i][j]<<"+";|code-block|syntax|javascript|1177040|entityMap^0|9|8|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

The simplest way would be to use <code>resize()</code> method as follow:

<pre><code>vector &lt;vector&lt;int&gt;&gt; v;
cin&gt;&gt;n&gt;&gt;m; //n is rows and m is columns
v.resize(n,vector&lt;int&gt;(m));
for(i=0;i&lt;n;i++) // inserts elements into the vector v
 for(j=0;j&lt;m;j++)
 cin&gt;&gt;v[i][j]; 

for(i=0;i&lt;n;i++) //accesses elements of vector v
 for(j=0;j&lt;m;j++)
 cout&lt;&lt;v[i][j]&lt;&lt;" ";
</code></pre>

I want to create 2D array using vector. But, when I do this, I get seg fault.
Can anyone please explain what I am doing wrong, and possible solution for this problem.

I made everything public since I dont want to deal with getters and setters now.
I want to get the concept of 2D array clear.

<pre><code>#include &lt;iostream&gt;
#include &lt;vector&gt;
using namespace std;

class point
{ 
 public:
 point():x(0),y(0){}
 ~point(){}
 point(float xx,float yy):x(xx),y(yy){}
 float x,y;
};

int main()
{
 vector&lt;vector&lt;point&gt; &gt; a; // 2D array
 point p(2,3);
 a[0][0] = p; // error here
 return 0;
}
</code></pre>

Two dimensional array using vector

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我想用向量来创建2D数组。但是，当我这样做的时候，我得到了seg错误。谁能解释一下我做错了什么，以及这个问题的可能解决方案。我公开了所有的东西，因为我现在不想和getter和setter打交道。我想弄清楚二维数组的概念。#include <iostream>#include <vector>using namespac...

问使用向量的二维数组
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