我不能使用hash_map :: operator []来读取哈希映射中的值？ [英] I cannot use the hash_map::operator[] to read the value in the hash map?
问题描述
>来自MSDN关于哈希映射的引用：
operator []将元素插入到具有指定
键值的hash_map中。 br />
给出了这样的例子：
hash_map< int，inthm1;
hm1 [2] = 40 ;
但是，没有如下例子：
int a = hm1 [2];
上面的行是否正确？
如果没有，如何实现函数读取对应的值
存储在哈希映射中的键2 ？
我正在寻找的就像Java的HashMap中的get（）方法。
>From the reference of MSDN about hash map:
operator[] Inserts an element into a hash_map with a specified
key value.
And such example is given:
hash_map <int, inthm1;
hm1[ 2 ] = 40;
However, there is no example like the following:
int a = hm1[2];
Is the line above correct at all?
If not, how to implement the function to read the value corresponding
to key 2 stored in the hash map?
What I am looking for is just like the get() method in HashMap of Java.
推荐答案
xz写道：
xz wrote:
>>来自MSDN关于哈希映射的引用：
>>From the reference of MSDN about hash map:
operator []将一个元素插入到一个带有指定
键值的hash_map中。
这样的前给出了足够的内容：
hash_map< int，inthm1;
hm1 [2] = 40;
operator[] Inserts an element into a hash_map with a specified
key value.
And such example is given:
hash_map <int, inthm1;
hm1[ 2 ] = 40;
like km1.put（2,40）;在Java
like km1.put(2, 40); in Java
>
但是，没有像下面这样的例子：
int a = hm1 [2];
>
However, there is no example like the following:
int a = hm1[2];
like int a =（int）hm1.get（2）;在Java
like int a = (int) hm1.get(2); in Java
>
上面的行是否正确？
如果没有，请如何实施读取存储在哈希映射中的键2对应值的函数
？
我正在寻找的就像get（）方法一样Java的HashMap。
>
Is the line above correct at all?
If not, how to implement the function to read the value corresponding
to key 2 stored in the hash map?
What I am looking for is just like the get() method in HashMap of Java.
8月1日晚上10点58分，Barry< dh ... @ 126.comwrote：
On Aug 1, 10:58 pm, Barry <dh...@126.comwrote:
xz写道：
xz wrote:
>来自MSDN关于哈希映射的引用：
>From the reference of MSDN about hash map:
operator []将元素插入到具有指定
键值的hash_map中。
operator[] Inserts an element into a hash_map with a specified
key value.
给出了这样的例子：
And such example is given:
hash_map< int ，inthm1;
hm1 [2] = 40;
hash_map <int, inthm1;
hm1[ 2 ] = 40;
喜欢km1.put（2,40）;在Java中
like km1.put(2, 40); in Java
但是，没有如下例子：
However, there is no example like the following:
int a = hm1 [2];
int a = hm1[2];
如int a =（int）hm1.get（2）;在Java中
like int a = (int) hm1.get(2); in Java
上面的行是否正确？
如果没有，如何实现该函数来读取相应的值
存储在哈希映射中的密钥2？
Is the line above correct at all?
If not, how to implement the function to read the value corresponding
to key 2 stored in the hash map?
我正在寻找的就像Java的HashMap中的get（）方法。
What I am looking for is just like the get() method in HashMap of Java.
谢谢。
我应该包含< hash_mapor< hash_map.h？
我认为它应该是
#include< hash_map>
但事实证明：
错误：hash_map：没有这样的文件或目录
Thanks.
And should I include <hash_mapor <hash_map.h?
I thought it should be
#include<hash_map>
but turns out:
error: hash_map: No such file or directory
8月1日晚上10点58分，Barry< dh ... @ 126.comwrote：
On Aug 1, 10:58 pm, Barry <dh...@126.comwrote:
xz写道：
xz wrote:
>来自MSDN的参考关于哈希映射：
>From the reference of MSDN about hash map:
operator []将元素插入到具有指定
键值的hash_map中。
operator[] Inserts an element into a hash_map with a specified
key value.
给出了这样的例子：
And such example is given:
hash_map< int ，inthm1;
hm1 [2] = 40;
hash_map <int, inthm1;
hm1[ 2 ] = 40;
喜欢km1.put（2,40）;在Java中
like km1.put(2, 40); in Java
但是，没有如下例子：
However, there is no example like the following:
int a = hm1 [2];
int a = hm1[2];
如int a =（int）hm1.get（2）;在Java中
like int a = (int) hm1.get(2); in Java
上面的行是否正确？
如果没有，如何实现该函数来读取相应的值
存储在哈希映射中的密钥2？
Is the line above correct at all?
If not, how to implement the function to read the value corresponding
to key 2 stored in the hash map?
我正在寻找的就像Java的HashMap中的get（）方法。
What I am looking for is just like the get() method in HashMap of Java.
错误：''class __gnu_cxx :: hash_map< double，double，
__gnu_cxx :: hash< double>， std :: equal_to< double>，std :: allocator< double>
error: ''class __gnu_cxx::hash_map<double, double,
__gnu_cxx::hash<double>, std::equal_to<double>, std::allocator<double>
>''没有名为''put'的成员'
>'' has no member named ''put''
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