cin.getline() 正在跳过 C++ 中的输入
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cin.getline() is skipping an input in C++
提问by theharshest
If I use the following code, getline doesn't take the last input(for last iteration of "for" loop, it simply skips it) -
如果我使用以下代码，getline 不会接受最后一个输入（对于“for”循环的最后一次迭代，它只是跳过它）-
int main()
{
int n;
map<string, set<string> > lst;
string c,s,c2;
cin>>n;
for(int i=0;i<n;i++)
{
getline(cin,c); // here it skips the input for last iteration
stringstream ss;
ss<<c;
bool f=1;
while(ss>>s)
{
if(f)
{
c2=s;
f=0;
}
else
lst[c2].insert(s);
}
}
for (map<string, set<string> >::const_iterator ci = lst.begin(); ci != lst.end(); ++ci)
{
cout<< (*ci).first <<" "<< (*ci).second.size() <<endl;
}
}
To get rid of it, I put cin.ignore() after getline. Now its taking all the inputs but I'm facing a new issue -
为了摆脱它，我将 cin.ignore() 放在 getline 之后。现在它接受了所有的输入，但我面临着一个新问题——
#include<iostream>
#include<string>
#include<map>
#include<set>
#include<sstream>
#include<algorithm>
using namespace std;
int main()
{
int n;
map<string, set<string> > lst;
string c,s,c2;
cin>>n;
for(int i=0;i<n;i++)
{
getline(cin,c);
cin.ignore();
stringstream ss;
ss<<c;
bool f=1;
while(ss>>s)
{
if(f)
{
c2=s;
f=0;
}
else
lst[c2].insert(s);
}
}
for (map<string, set<string> >::const_iterator ci = lst.begin(); ci != lst.end(); ++ci)
{
cout<< (*ci).first <<" "<< (*ci).second.size() <<endl;
}
}
The new issue is that while taking c2, first character of string gets removed. For example, if I give "England Jane Doe" as input to getline, in c2 I'll get "ngland".
新问题是在取 c2 时，字符串的第一个字符被删除。例如，如果我将“England Jane Doe”作为 getline 的输入，在 c2 中我将得到“ngland”。
How to get rid of this issue now?
现在如何摆脱这个问题？
回答by Martin York
This:
这个：
cin>>n;
Is reading the number only.
It leaves the trailing '\n'on the stream.
只读取数字。
它'\n'在流上留下尾随。
So your first call to getline()is reading an empty line containing just a '\n'
所以你的第一个调用getline()是读取一个只包含一个的空行'\n'
It is best not to mix the use of operator>>and std::getline(). You have to be very careful on whether you have left the newline on the stream. I find it easiest to always read a line at a time from a user. Then parse the line separately.
最好不要混合使用operator>>和std::getline()。你必须非常小心你是否在流中留下了换行符。我发现每次从用户那里读取一行是最容易的。然后分别解析该行。
std::string numnber;
std::getline(std::cin, number);
int n;
std::stringstream numberline(number);
numberline >> n;
回答by Ben Cottrell
your cin.ignore()is in the wrong place. getline does not leave the trailing \nnewline character, it's the >>symbol which does that.
你cin.ignore()在错误的地方。getline 不会留下尾随的\n换行符，它是>>这样做的符号。
What you probably want is
你可能想要的是
cin>>n;
cin.ignore();
回答by Vikas Kalwani
just write
写就好了
cin.ignore();
after your last ">>" operator. ">>" operator leaves a newline "\n" in the input bitstream which needs to be cleared before taking the inputs.
在最后一个“>>”运算符之后。">>" 操作符在输入比特流中留下一个换行符 "\n"，在输入之前需要清除它。
回答by Rajeev
actually the cin buffer has \n remaining from last cin, so getline take this \n character and gets terminated; ignore the content of buffer before getline...
实际上 cin 缓冲区从最后一个 cin 中还剩下 \n，所以 getline 使用这个 \n 字符并被终止；在getline之前忽略缓冲区的内容...
cin.ignore();
cin.ignore();
getling(cin, string_name);
getling(cin, string_name);
//it will work smoothly
//它会顺利运行
