Counting Occurrences of integers in map c++ [closed] - c++

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I am trying to see if there are any duplicates of integers as I am inserting them using map because it`s auto sorting them when the numbers are inserted.
For example when I insert integers in the following order : 2 3 2 4 5
I want an output like : at least a number is duplicated , ` I have tried many things but no success, any ideas?
The problems I am facing is this: You have a array of type integers and you have to find if there are any duplicates using map .

Answer 1

Use map::find
int keyToInsert = 2;
std::map<int, int>::iterator it;
it = yourMap.find(key);
if(it != yourMap.end()){
//alert user key exists
}
else {
//key doesn't exist
}
See docs: http://www.cplusplus.com/reference/map/map/find/

Answer 2

The way you are approaching the problem seems fundamentally wrong. std::map is a data structure used to "map" logical entities in a container.
for example it can be used to map names to phone numbers. like this:
{ ("Tom", 2344556), ("Amanda", 545654), ...}
that would be an example of std::map<std::string,int> .
a map is NOT used for keeping seperate int values together. if you want that functionality you should look into other containers.
If you want to use a container that keeps values in order (and keeps duplicates) you can use std::list or std::vector, if you want a data structure where order is not guaranteed but access is fast and duplicates are generally avoided, you can use std::set

Answer 3

I think you want something like (untested code):
bool check_for_duplicate(const std::map<my_key_type, int>& my_map)
{
std::set<int> my_set;
for (auto& i : my_map)
{
if (!my_set.insert(i.second).second) // If it failed to insert
return true;
}
return false;
}

Answer 4

Idea is to take "integers" as key and "number of repetition " as value of map .By doing so , you will not only able to figure out whether it a number was repeated but you would also figure out "how many times was it actually repeated " .I am sharing below code snippet .
#include <iostream>
#include <map>
using namespace std;
int main ()
{
int arr[10] = {1,2,3,4,1,2,2,1,4,5};
std::map<int,int> dup_map;
for(int i=0;i<=9;i++)
{
if(dup_map.find(arr[i])!=dup_map.end())
{
//key exist and hence update the dulpicate count;
dup_map[arr[i]]++;
}
else{
//it doesn't exist in map
dup_map.insert(std::pair<int,int>(arr[i],1));//single count of current number
}
}
for(std::map<int,int>::iterator it =dup_map.begin();it!=dup_map.end();it++)
{
cout<<"\n Number "<<it->first<<" is repeated "<<it->second<<" times ";
}
}
Output of the program is as below :
Number 1 is repeated 3 times
Number 2 is repeated 3 times
Number 3 is repeated 1 times
Number 4 is repeated 2 times
Number 5 is repeated 1 times