我想知道，我的代码有什么问题。我无法打印正确的乘法值。 [英] I want to know, what is wrong in my code. I cannot print proper multiplication value.
问题描述
int i=0,j=0,k=0,l=0,m=0,n=0,q=0,prod=0;
int a[3][3],b[3][3],s[3][3];
int *p;
////////////////////////////////////////////////////////////////////////////// INITIALIZING FIRST MATRIX
printf("Enter the first matrix \n \n");
while(i<3)
{
j=0;
while(j<3)
{
scanf("%d",&a[i][j]);
j++;
}
i++;
}
printf("\n");
/////////////////////////////////////////////////////////////////////////// DISPLAYING FIRST MATRIX
p=&a[0][0];
printf("The first matrix is \n\n");
i=0;
while(i<3)
{
j=0;
while(j<3)
{
printf("%d \t ",*(p+i*3+j));
j++;
}
printf("\n");
i++;
}
printf("\n");
////////////////////////////////////////////////////////////////////////// INITIALIZING SECOND MATRIX
printf("Enter the second matrix \n \n");
while(k<3)
{
l=0;
while(l<3)
{
scanf("%d",&b[k][l]);
l++;
}
k++;
}
printf("\n");
////////////////////////////////////////////////////////////////////////// DISPLAYING SECOND MATRIX
p=&b[0][0];
printf("The second matrix is \n\n");
k=0;
while(k<3)
{
l=0;
while(l<3)
{
printf("%d \t",*(p+k*3+l));
l++;
}
printf("\n");
k++;
}
printf("\n");
////////////////////////////////////////////////////////////////////// CALCULATING MATRIX MULTIPLICATION
for(m=0;m<3;m++){
for(n=0;n<3;n++)
{
for(q=0;q<3;q++){
prod=prod+a[i][q]*b[q][l];
}
s[m][n] = prod;
prod=0;
}
}
printf("Resultant matrix : \n");
for(m=0;m<3;m++)
{
for(n=0;n<3;n++)
printf("%d ",s[m][n]);
printf("\n");
}
return 0;
}
我的尝试：
成功获取并打印矩阵值但提供不正确的乘法值
What I have tried:
successfully takes and prints matrix value but gives incorrect multiplication value
推荐答案
您的乘法步骤
Your multiplication step
for(m=0;m<3;m++){
for(n=0;n<3;n++)
{
for(q=0;q<3;q++){
prod=prod+a[i][q]*b[q][l];
}
s[m][n] = prod;
prod=0;
}
}
错误。
尝试
is wrong, indeed.
Try
for(m=0;m<3;m++)
{
for(n=0;n<3;n++)
{
s[m][n] = 0;
for(q=0;q<3;q++)
{
s[m][n] += a[m][q]*b[q][n];
}
}
}
i的值是多少？ / code>和 l 在此代码中？
What are the values ofiandlin this code?
prod=prod+a[i][q]*b[q][l];
它应该是什么？
你的代码不按你期望的方式运行，或者你不明白为什么！
有一个几乎通用的解决方案：逐步在调试器上运行代码，检查变量。
调试器在这里向您展示您的代码正在做什么，您的任务是与它应该做什么进行比较。
调试器中没有魔法，它不知道你的代码应该做什么，它没有找到错误，它只是通过向你展示正在发生的事情来帮助你。当代码没有达到预期的效果时，你就接近了一个错误。
要查看你的代码在做什么：只需设置断点并查看代码是否正常运行，调试器允许你执行第1行第1行，并在执行时检查变量。
调试器 - 维基百科，免费的百科全书 [ ^ ]
掌握调试Visual Studio 2010 - 初学者指南 [ ^ ]
使用Visual Studio 2010进行基本调试 - YouTube [ ^ ]
1.11 - 调试程序（步进和断点）|学习C ++ [ ^ ]
调试器仅显示您的代码正在执行的操作，您的任务是与应该执行的操作进行比较。
Is it what it should be ?
Your code do not behave the way you expect, or you don't understand why !
There is an almost universal solution: Run your code on debugger step by step, inspect variables.
The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't know what your code is supposed to do, it don't find bugs, it just help you to by showing you what is going on. When the code don't do what is expected, you are close to a bug.
To see what your code is doing: Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute.
Debugger - Wikipedia, the free encyclopedia[^]
Mastering Debugging in Visual Studio 2010 - A Beginner's Guide[^]
Basic Debugging with Visual Studio 2010 - YouTube[^]
1.11 — Debugging your program (stepping and breakpoints) | Learn C++[^]
The debugger is here to only show you what your code is doing and your task is to compare with what it should do.
编译并不意味着您的代码是正确的！ ：笑：
将开发过程想象成编写电子邮件：成功编译意味着您使用正确的语言编写电子邮件 - 例如英语而不是德语 - 而不是电子邮件包含您的邮件想发送。
所以现在你进入第二阶段的发展（实际上它是第四或第五阶段，但你将在之后的阶段进入）：测试和调试。
首先查看它的作用，以及它与你想要的有何不同。这很重要，因为它可以为您提供有关其原因的信息。例如，如果程序旨在让用户输入一个数字并将其翻倍并打印答案，那么如果输入/输出是这样的：
Compiling does not mean your code is right! :laugh:
Think of the development process as writing an email: compiling successfully means that you wrote the email in the right language - English, rather than German for example - not that the email contained the message you wanted to send.
So now you enter the second stage of development (in reality it's the fourth or fifth, but you'll come to the earlier stages later): Testing and Debugging.
Start by looking at what it does do, and how that differs from what you wanted. This is important, because it give you information as to why it's doing it. For example, if a program is intended to let the user enter a number and it doubles it and prints the answer, then if the input / output was like this:
Input Expected output Actual output
1 2 1
2 4 4
3 6 9
4 8 16然后很明显问题出在将它加倍的位 - 它不会将自身加到自身上，或者将它乘以2，它会将它自身相乘并返回输入的平方。
所以，你可以查看代码和很明显，它在某处：
Then it's fairly obvious that the problem is with the bit which doubles it - it's not adding itself to itself, or multiplying it by 2, it's multiplying it by itself and returning the square of the input.
So with that, you can look at the code and it's obvious that it's somewhere here:
int Double(int value)
{
return value * value;
}
一旦你知道可能出现的问题，就开始使用调试器找出原因。在方法的第一行放置一个断点，然后运行你的应用程序。当它到达断点时，调试器将停止，并将控制权移交给您。您现在可以逐行运行代码（称为单步执行）并根据需要查看（甚至更改）变量内容（哎呀，您甚至可以更改代码并在需要时再试一次）。 />
在执行代码之前，请考虑代码中的每一行应该做什么，并将其与使用Step over按钮依次执行每一行时实际执行的操作进行比较。它符合您的期望吗？如果是这样，请转到下一行。
如果没有，为什么不呢？它有什么不同？
希望这可以帮助你找到代码的哪个部分有问题，以及问题是什么。
这是一项技能，它是一个值得开发的，因为它可以帮助你在现实世界和发展中。和所有技能一样，它只能通过使用来改善！
并帮自己一个忙：停止使用一个角色名称。键入可能更快，但它使您的代码更难阅读。使用描述性名称（反映对象包含的数据的名称）和您的代码开始变为自我记录，这可以显着减少错误的数量，并使您在回到它时更容易几周时间......
Once you have an idea what might be going wrong, start using the debugger to find out why. Put a breakpoint on the first line of the method, and run your app. When it reaches the breakpoint, the debugger will stop, and hand control over to you. You can now run your code line-by-line (called "single stepping") and look at (or even change) variable contents as necessary (heck, you can even change the code and try again if you need to).
Think about what each line in the code should do before you execute it, and compare that to what it actually did when you use the "Step over" button to execute each line in turn. Did it do what you expect? If so, move on to the next line.
If not, why not? How does it differ?
Hopefully, that should help you locate which part of that code has a problem, and what the problem is.
This is a skill, and it's one which is well worth developing as it helps you in the real world as well as in development. And like all skills, it only improves by use!
And do yourself a favour: stop using one character names. It maybe quicker to type, but it makes your code a lot harder to read. Use descriptive names (ones that reflect what data the object contains) and your code starts to become self documenting, and that can reduce the number of errors significantly, as well as making it a lot easier for you when you come back to it in a couple of weeks time...
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