为什么它显示错误的答案。 [英] Why it is showing wrong answer.
问题描述
您将获得一个数字N.您需要在最小操作数量下将其转换为1.
允许的操作如下：
如果N是偶数则将数字除以2.
如果N为奇数，则可以向其中加1或从中减去1.
第一行输入包含T表示测试用例的数量。随后是T测试用例。每个测试用例包含1行包含N的输入。
我尝试过：
You are given a number N. You need to convert it to 1 in minimum number of operations.
The operations allowed are as follows:
If N is even then divide the number by 2.
If N is odd then you can either add 1 to it or subtract 1 from it.
The first line of input contains T denoting the number of testcases. T testcases follow. Each testcase contains 1 line of input containing N.
What I have tried:
#include<bits/stdc++.h>
using namespace std;
int p(int x)
{
int z=0;
while(x)
{
if(x&1)
z++;
x>>=1;
}
if(z==1)
return z;
return 0;
}
int main()
{
int t;
cin>>t;
while(t--)
{
int n,ctr=0;
cin>>n;
if(n==1)
ctr=0;
else
{
while(n>1)
{
if(n%2==0)
{
ctr++;
n/=2;
}
else
{
if(p(n-1))
n-=1;
else if(p(n+1))
n+=1;
else
n-=1;
ctr++;
}
}
}
cout<<ctr<<endl;
}
return 0;
}
推荐答案
编译并不意味着你的代码是对的！ ：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进！
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!
您需要调试代码。一些重要的提示：
1.使用大括号每个单个IF / ELSE语句并对齐代码
（我希望现在很清楚）
2.在返回的情况下做一些输出。
3.写一些测试代码*
4最后但并非最不重要：使用调试人员
*您需要使用主代码中的while代码生成函数。
You need to debug your code. Some important tips:
1. use braces for EVERY SINGLE IF/ELSE STATEMENT and align the code
(I hope it is clear now)
2. make some output in the return cases.
3. write some test code*
4. last but not least: USE THE DEBUGGER
*you need to make function from the while code in your main.
为什么显示错误的答案。
Why it is showing wrong answer.
当询问时这类问题，最好用实际答案和预期答案显示几个样本数据。由于它看起来像一个网站的挑战，提供链接也是一个好主意。
学会正确缩进你的代码，它显示其结构，它有助于阅读和理解。它还有助于发现结构错误。
When asking this kind of question, it is a good idea to show a couple sample data with actual answer and expected one. Since it looks like a challenge from a site, it is also a good idea to give link.
Learn to indent properly your code, it show its structure and it helps reading and understanding. It also helps spotting structures mistakes.
#include<bits/stdc++.h>
using namespace std;
int p(int x)
{
int z=0;
while(x)
{
if(x&1)
z++;
x>>=1;
}
if(z==1)
return z;
return 0;
}
int main()
{
int t;
cin>>t;
while(t--)
{
int n,ctr=0;
cin>>n;
if(n==1)
ctr=0;
else
{
while(n>1)
{
if(n%2==0)
{
ctr++;
n/=2;
}
else
{
if(p(n-1))
n-=1;
else if(p(n+1))
n+=1;
else
n-=1;
ctr++;
}
}
}
cout<<ctr<<endl;
}
return 0;
}
缩进风格 - 维基百科 [ ^ ]
专业程序员的编辑有这个功能和其他功能，如括号匹配和语法高亮。
Notepad++主页 [ ^ ]
ultraedit [ ^ ]
你的代码行为不像你期待，或者你不明白为什么！
有一个几乎通用的解决方案：一步一步地在调试器上运行你的代码，检查变量。
调试器在这里向您展示您的代码正在做什么你的任务是与应该做的比较。
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bug，它只是通过向您展示正在发生的事情来帮助您。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Visual Studio 2010中的调试 - 初学者指南 [ ^ ]
使用Visual Studio 2010进行基本调试 - YouTube [ ^ ]
1.11 - 调试程序（踩踏和断点）|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。
[更新]
建议：学习检查你的代码（这是工作的一部分）。
改变你的程序列出集合为解决每个值而执行的操作。
对于此问题，请设置值为1,2,3,4,5,6,7,8,9的样本集......
写下基数2中的值并写下减少的每一步，也用基数2写。
手工求解，用你的程序求解，比较结果。
看到你有差异时，尝试发现一个模式，使用调试器来查看你的程序在做什么，有时它不像你那样。
Indentation style - Wikipedia[^]
Professional programmer's editors have this feature and others ones such as parenthesis matching and syntax highlighting.
Notepad++ Home[^]
ultraedit[^]
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.
[Update]
Advice: Learn to check your code (it is part of the job).
change your program to list the set of operations done to solve each values.
For this problem, make a sample set with values 1, 2, 3, 4, 5, 6, 7, 8, 9 ...
write the values in base 2 and write each step of reduction and with base 2 too.
solve by hand, and solve with your program, compare results.
See when you have differences, try to spot a pattern, use the debugger to see what your program is doing, sometime it don't do like you by hand.
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