occurring letters queued

#include<bits/stdc++.h>
using namespace std;
int main()
{
    long long int i,j,k=0,m,n;
     long long int a,b;
   string s,c,ch;
   getline(cin,s);
   c = s;
   n= s.length();

   int ar[n+1] = {0};
   set<char>  mp;
   set<char> ::iterator it;
  for(i=0;i<n;i++)
  {
      for(j=i+1;j<n;j++)
      {
          if(s[i]==s[j])
          {
              s[j] ='\0';
          }
      }
  }
  for(i=0;i<s.length();i++)
  {

          s.erase(std::remove(s.begin(), s.end(), '\0'), s.end());

  }
  for(i=0;i<s.length();i++)
  {
      k = count(c.begin(),c.end(),s[i]);
      if(s[i]==' ')
      {
           cout<<"SPACE = "<<k<<endl;
      }
      else
      cout<<s[i] <<" = "<<k<<endl;
  }

}