[英]Concatenating two 3 by 3 arrays into one array in C++
As the title indicates, I want to concatenate two arrays into one larger array. 如标题所示,我想将两个数组连接成一个更大的数组。 for example:
例如:
array1= 1 2 3
4 5 6
7 8 9
array1= 10 20 30
40 50 60
70 80 90
array3= 1 2 3 10 20 30
4 5 6 40 50 60
7 8 9 70 80 90
So, I wrote this code: 因此,我编写了以下代码:
#include <iostream>
using namespace std;
int main()
{
int array1[3][3],array2[3][3],array3[3][6];
int i,j;
//Matrix 1 input
cout<<"Enter matrix 1\n";
for (i=0;i<3;i++)
{
for (j=0;j<3;j++)
{
cin>>array1[i][j];
array3[i][j]=array1[i][j]; //Assigning array1 values to array3
}
}
//array2 input
cout<<"Enter matrix 2\n";
for (i=0;i<3;i++)
{
for (j=3;j<6;j++)
{
cin>>array2[i][j];
array3[i][j]=array2[i][j]; //Assigning array2 values to array3
}
}
//array3 output
cout<<"New matrix is\n";
for (i=0;i<3;i++)
{
for (j=0;j<6;j++)
{
cout<<array3[i][j]<<"\t";
}
cout<<"\n";
}
}
But when I execute it, I ended up with last row of array2 being the (2,3), (2,4) and (2,5) elements (which is right), but also being the (0,1), (0,2) and (0,3) elemnts (which should be [1 2 3]). 但是,当我执行它时,我最后得到array2的最后一行是(2,3),(2,4)和(2,5)元素(是正确的),但也是(0,1), (0,2)和(0,3)元素(应为[1 2 3])。
array3= 70 80 90 10 20 30
4 5 6 40 50 60
7 8 9 70 80 90
So, what's happening here? 那么,这是怎么回事?
EDIT: I did the following: 编辑:我做了以下:
for (i=0;i<3;i++)
{
for (j=0;j<3;j++)
{
cin>>array2[i][j];
array3[i][j+3]=array2[i][j]; //Assigning array2 values to array3 and adding 3 to j
}
And it went ok. 一切顺利。 Is the method I used "professional"?
我使用的方法是“专业”吗? }
}
This is undefined behavior: 这是未定义的行为:
for (i=0;i<3;i++)
for (j=3;j<6;j++)
array3[i][j]=array2[i][j];
array2
is 3x3 but you're indexing into it starting with [0][3] which is an error. array2
是3x3,但是您array2
[0] [3]开始对其进行索引,这是一个错误。 You could get runtime checking of this sort of thing if you used C++11 std::array
and its .at()
method instead of raw C arrays. 如果使用C ++ 11
std::array
及其.at()
方法而不是原始C数组,则可以对这种情况进行运行时检查。
array2
is a 3x3 array and you use j indices between 3 and 6 : you access outside of your matrix anywhere in memory. array2
是一个3x3数组,您使用3到6之间的j索引:您可以在矩阵的外部访问内存中的任何位置 。
You should instead write (eg) : 您应该改写(例如):
//array2 input
cout<<"Enter matrix 2\n";
for (i=0;i<3;i++)
{
for (j=0;j<3;j++)
{
cin>>array2[i][j]; // j is correct for array2
array3[i][j+3]=array2[i][j]; //Assigning array2 values to array3
}
}
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