cin.getline()在C ++中跳过一个输入 [英] cin.getline() is skipping an input in C++
问题描述
如果我使用下面的代码,getline不接受最后一个输入(对于for循环的最后一次迭代,它只是跳过它) -
If I use the following code, getline doesn't take the last input(for last iteration of "for" loop, it simply skips it) -
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;
}
}
为了摆脱它,我把cin.ignore ()在getline之后。现在它接受所有的输入,但我面临一个新的问题 -
To get rid of it, I put cin.ignore() after getline. Now its taking all the inputs but I'm facing a new issue -
#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;
}
}
新问题是,的字符串被删除。例如,如果我给England Jane Doe作为getline的输入,在c2中我将得到ngland。
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".
如何摆脱这个问题?
推荐答案
cin>>n;
仅读取数字。
它留下的尾部<$ c $
Is reading the number only.
It leaves the trailing '\n'
on the stream.
因此,您第一次调用 getline()
正在读取只包含'\\\
'
So your first call to getline()
is reading an empty line containing just a '\n'
的空行混合使用 operator>>
和 std :: getline()
。你必须非常小心,你是否已离开换行。我发现最容易总是从用户读取一行。
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.
std::string numnber;
std::getline(std::cin, number);
int n;
std::stringstream numberline(number);
numberline >> n;
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