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  • [ ] 自动插入map

    performing an insertion if such key does not already exist.

    #include <iostream>
    #include <map>
     
    int main()
    {
        std::map<char, int> letter_counts;
     
        letter_counts['a'];
        for(auto& [k,v]: letter_counts) {
            std::cout<<k <<", "<<v<<std::endl; 
        }
        std::cout<<"-------------------"<<std::endl;
        letter_counts['b'];
        for(auto& [k,v]: letter_counts) {
            std::cout<<k <<", "<<v<<std::endl; 
        }
        std::cout<<"-------------------"<<std::endl;
        letter_counts['a']=1;
        for(auto& [k,v]: letter_counts) {
            std::cout<<k <<", "<<v<<std::endl; 
        }
        std::cout<<"-------------------"<<std::endl;
        letter_counts['a'];
        for(auto& [k,v]: letter_counts) {
            std::cout<<k <<", "<<v<<std::endl; 
        }
        std::cout<<"-------------------"<<std::endl;
    
        return 0;
    }
    

    output:

    a, 0
    
    -------------------
    
    a, 0
    
    b, 0
    
    -------------------
    
    a, 1
    
    b, 0
    
    -------------------
    
    a, 1
    
    b, 0
    
    -------------------
    
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  • 原文地址:https://www.cnblogs.com/Searchor/p/15465938.html
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