Differentiate between a substring, a subsequence, and a subset

// C++ program to print all possible
// substrings of a string
#include<iostream>
using namespace std;
void find_subStrings(string & str, int start, int end){
  if (start > end) {
    return;
  }
  for (int i = start; i <= end; i++){
    cout << str.substr(start, i - start + 1) << endl;
  }
  find_subStrings(str, start + 1, end);
}
// Driver code
int main(){
  string str = "fruitcakes";
  int n = str.length();
  cout << "The total number of elements in the string: " << str.length() << endl;
  find_subStrings(str,0,n-1);
  cout << "The total number of substrings = " << n * (n + 1)/2 << endl;
  return 0;
}

// C++ program to print all possible
// subsequences of a string
 
#include<iostream>
#include<math.h>
using namespace std;
 
// Function to print all sub strings
void find_subSequences(string & str, string result, int i){
    // base case
    if (i == str.length()){
        if(result != "")
            cout << result << endl;
        return;
    }
    find_subSequences(str, result + str[i], i+1);
    find_subSequences(str, result, i+1);
}
 
// Driver code
int main(){
    string str = "fruitcakes";
    string result = "";
    cout << "The total number of elements in the string: " << str.length() << endl;
    find_subSequences(str, result, 0);
    cout << "The total number of subsequences = " << pow(2,str.length()) - 1 << endl;
    return 0;
}

// C++ program to print all possible 
// subsets of a set
 
#include<iostream>
#include <vector>
using namespace std;
// Helper function to print results
void PrintList(vector<string>& subset){
    string out = "[";
    for (int i = 0; i < subset.size(); i++) out+= subset[i] + ", ";
    out = out.substr(0, out.length() -2);
    out += "]";
    cout << out << endl;
}
 
void find_subSets(vector<string>& set, vector<vector<string>>& subsets, vector<string>& subset, int index){
    // base case
    if (index == set.size()){
        subsets.push_back(subset);
        return;
    }
    find_subSets(set, subsets, subset, index + 1);
    subset.push_back(set[index]);
    find_subSets(set, subsets, subset, index + 1);
    subset.pop_back();
}
vector<vector<string>> getAllSubsets(vector<string>& set){
    vector<vector<string>> subsets;
    vector<string> subset;
    find_subSets(set, subsets, subset, 0);
    return subsets;
}
 
// Driver code
int main(){
    vector<string> set = {"java", "python", "react", "ruby", "solidity"};
    cout << "The total number of elements in the set: " << set.size() << endl;
    vector<vector<string>> result = getAllSubsets(set);
    for (auto it : result){
        PrintList(it);
    }
    cout << "The total number of subsets = " << result.size() << endl;
    return 0;
}