c++ - 找不到我存储到地图中的值

问题描述

我基本上是逐个字符地读取文件，当我遇到一个新数字时，我将它std::map作为一个元素存储在一个键中，元素等于 1。我遇到相同数字的次数越多，我就会增加该键的元素：

if(intMap.count(singleCharacter)){
    //keyexist  just increment count else
    //cout<<"exist"<<endl;
                
    int newValue =  intMap.at(singleCharacter) + 1; //grabs the value that already exists and we need to incrmenet it by 1 and store the new value in the map.

    std::map<int, int>::iterator it = intMap.find(singleCharacter); //finds the single character and increments it by 1.

    if (it != intMap.end())
        it->second = newValue; //setting the new increment value into the element
}else{
    //doesnt exist and and we need to create it and incrmenet by 1
    //cout<<"doesnt exist"<<endl;
    intMap.insert(pair<int, int>(singleCharacter,1));
    cout<<singleCharacter <<" new made : "<<intMap.at(singleCharacter) <<endl;
    }
}

for (auto& p : intMap ) {
    cout << p.first<<": "<< p.second <<endl;; // "Karl", "George"
}

唯一的问题是，当我尝试打印地图中的所有值时，它给了我随机数，我不明白它们来自哪里。

这是我正在阅读的文件：

An International Standard Book Number (ISBN) is a code of 10 characters, referred to as ISBN-10,                                                                             
 separated by dashes such as 0-7637-0798-8. An ISBN-10 consists of four parts: a group code, a publisher code,                                                                
 a code that uniquely identifies the book among those published by a particular publisher, and a check character.                                                             
 The check character is used to validate an ISBN. For the ISBN 0-7637-0798-8, the group code is 0,                                                                            
 which identifies the book as one from an English-speaking country. The publisher code 7637 is for "Jones and Bartlett Publishers

我得到的输出：

我应该得到的输出应该是：

1: and the amount of times it was seen

这对任何数字都是一样的。

标签： c++

你得到那些“随机”数字是因为你使用的是std::map<int,int>而不是std::map<char,int>. 您打印的是字符符号的 ASCII 数字代码及其计数。

So, you need to either change the map's type, or cast the keys back to char:

for (auto& p : intMap ) {
    cout << static_cast<char>(p.first) << ": "<< p.second <<endl;
}

Note: std::map::operator[] is precisely designed for such case, it will initialize missed values with 0 in this case, so all of your conditions can be replaced with:

intMap[singleCharacter]++;

Details can be found in this documentation.

c++ - 找不到我存储到地图中的值

问题描述

解决方案

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