How to check and print repeat values in a vector

Question

I have the following problem to check the repeating vectors in a Vector:

Given a sequence of n real numbers, determine the numbers that make up the sequence and the number of times each of them occurs in it.

Example:

n = 8

Sequel:

-1.7, 3.0, 0.0, 1.5, 0.0, -1.7, 2.3, -1,7

Exit:

-1.7 occurs 3 times

3.0 occurs 1 time

0.0 occurs 2 times

1.5 occurs 1 time

2.3 occurs 1 time

Here’s the code I wrote so far in C++:

#include <iostream>
using namespace std;
int main () {
	int n, i, i2, i3, a, cont=0;
	cin>>n;
	float vet[n], vet2[n], vet3[n];
	for(i=0 ; i<n ; i++){
		cin>>vet[i];
		vet2[i]=vet[i];
	}
	for(i=0 ; i<n ; i++){
		cont=0;
		for(i2=0 ; i2<n ; i2++){
			if(vet[i]==vet2[i2]){
				cont++;
				vet3[i]=vet[i];
			}
		}
		cout.precision(1);
		cout<<fixed<<vet[i]<<" ocorre "<<cont<<" vezes"<<endl;		
	}
			
	
	return 0;
}	

So far I’m having the following result:

the problem is that the repeated values are being shown in the amount of times they contain within the vector, and not just one as asks for the exercise.

:/

Answer 1

The problem is that you are assigning an 8 value to N, let’s say your vector:

vet[0] = -1.7
vet[1] = 3
vet[2] = 0
vet[3] = 1.5
vet[4] = 0
vet[5] = -1.7
vet[6] = 2.3
vet[7] = -1.7

So every time he will check, because in his for he will go through this vector 8 times, for example in his case at position 0 5 and 7 of his vector, we have the value -1.7, so when he falls in the second for it will do this check at positions 0, 5 and 7. Also note that your command to print cout is just after the second repeat command ends and before the first will start again then it will print all 8 times.

Answer 2

There is a "C++ way that is not C" to do some things, whenever you can use C++ prefer :

1 - Use containers stl : Std::vector instead of vectors "float vet[n]", because the allocation and misallocation are automatic.

2 - Use Std::map for values that must be "indexed" by search keys

vector<float> vet;
map<float, int> result;

3 - Use stl algorithms and iterators instead of "for ( int.." pq makes clear your intention ) Std::copy, Std::Transform, Std::find... for example to copy n elements of an entry use Std::copy_n( in... ), to insert into an array, use Std::back_inserter :

copy_n(istream_iterator<float>(in), n, back_inserter(vet));  // le n elementos float de in e insere no vetor.

4 - Maps are native search structures: The bottom line has 2 commands: one is result[v] that searching v in result, if not found creates a default int() (initialized with 0) on the map with the 'v' key that you used to search and returns a reference to it, if it finds returns a reference to the found item, anyway, the map ensures that there will be a valid reference in the answer. The other part is ++ that will run in the result of the first part. Adding perfectly 1 in the item you are looking for.

++result[v]

5 - To generate the result the is standard maps :

 for( const auto& [k, v] : result) {
   cout << k << " -> " << v << endl;
 }

Example in Compiler explorer https://godbolt.org/z/MzPcc1

Answer 3

Buddy, I haven’t programmed for C in a while, but I did what you need in javascript, the logic is the same

var array = [1,2,3,2,4,5,6,3,6,8,7,4]
var arrayVerificado = [];

for(var i = 0; i < array.length; i++){
	var contador = 0;  
  var repetiu = false;
  
  for(var z = 0; z < arrayVerificado.length; z++){
  	if(arrayVerificado[z] == array[i]){
     //Verifico se no array auxiliar, o número já foi verificado, caso sim, seto a variavel repetiu para true.
    	repetiu = true
    }
  }  
  if(repetiu == false){ //caso não tenha repetido, eu deixo o padrão false.
  arrayVerificado.push(array[i])//add no meu array auxiliar que este número vai ser verificado
    for(var j = 0; j < array.length; j++){
      if(array[i] == array[j]){ //se ele achar, faço meu contador acrescentar +1
        contador++
      }
      
    }
      console.log("O número: "+ array[i]+ " repetiu: "+ contador + " vezes");
      }

}