How can I desc order in vectors C-CodePudding

I have C code like below.

It works well but my output like this :

192.168.1.163 => 4 times 
192.168.1.165 => 7 times 
192.168.1.20 => 62 times

How can I make desc order like :

192.168.1.20 => 62 times 
192.168.1.165 => 7 times 
192.168.1.163 => 4 times

    std::map<std::string, int> stringCount; //str is ip and int is logged count
    
    while(std::getline(readIp, ipLine))//go line by line
    {
        std::istringstream ss(ipLine);
        ipLine.erase(std::remove(ipLine.begin(), ipLine.end(), '"'), ipLine.end()); //removed "

        stringCount[ipLine]  ; //increment the count 
    }
    readIp.close();
    std::cout<<"Total number of ip's are logged on the system :"<<stringCount.size()<<std::endl;
    std::ofstream outputFile("times.txt");
    
    for(std::pair<std::string, int> pairElement: stringCount)
    {
        std::cout<<pairElement.first<<" => "<<pairElement.second<<" times "<<std::endl;
        outputFile<<pairElement.first<<" => "<<pairElement.second<<" times \n";
    }

CodePudding user response：

Since it is not possible to sort a std::map by its values you can use something like a std::vector as shown below. The program below writes the ip addresses in decreasing order of count values as you want.

#include <iostream>
#include <map>
#include <sstream>
#include <fstream>
#include <vector>
#include <algorithm>
//create a function that will be used as comparator
bool sortInDecreasingOrder(std::pair<std::string, int> const &a, std::pair<std::string, int> const &b)
{
    return a.second > b.second;
}

int main() {
    
    //this map maps each word in the file to their respective count
    std::map<std::string, int> stringCount;
    std::string word, line;
    int count = 0;//this count the total number of words
    
    std::ifstream inputFile("log.txt");
    if(inputFile)
    {
        while(std::getline(inputFile, line))//go line by line
        {
            std::istringstream ss(line);
            
            //increment the count 
            stringCount[line]  ;
            
        }
    }
    else 
    {
        std::cout<<"File cannot be opened"<<std::endl;
    }
    
    inputFile.close();
    
    std::cout<<"Total number of unique ip's are:"<<stringCount.size()<<std::endl;
    
    
    //since we cannot sort a std::map by its second value we can create a vector and sort that vector 
    std::vector<std::pair<std::string, int>> vec(stringCount.begin(), stringCount.end());
    
    //now you can sort this vector 
    std::sort(vec.begin(), vec.end(), sortInDecreasingOrder);
    
    //lets create a output file and write into it the unique ips 
    std::ofstream outputFile("code.txt");
    
    
    for(std::pair<std::string, int> pairElement: vec)//note this time we go through vector vec instead of map
    {
        std::cout<<pairElement.first<<" => "<<pairElement.second<<" times "<<std::endl;
        outputFile<<pairElement.first<<" => "<<pairElement.second<<" times \n";
      
    }
    outputFile.close();
    return 0;
}

The output of the program can be seen here.