检查给定字符串是否可以由其他两个字符串或它们的排列组成

//including the required libraries
#include <bits/stdc++.h>
using namespace std;

//check if string can be formed by permutations of two strings
bool permutation( string str,vector<string> arr) {
   int size = arr.size();

   //sorting the given string
   sort(str.begin(), str.end());

   //extracting two strings at a time
   for (int i = 0; i < size - 1; i++) {
      for (int j = i + 1; j < size; j++) {

         //concatenate the pair of string
         string concat = arr[i] + arr[j];

         // Sort the resultant string
         sort(concat.begin(), concat.end());

         //comparing if the order of characters in both strings are same
         if (concat.compare(str) == 0) {

            //if equal
            return true;
         }
      }
   }

   //no such combination exists
   return false;
}
int main(){

   //declaring the input string
   string str = "tutorials";

   //array of strings
   vector<string> arr{ "trils", "outa", "ginc", "abc" };
   bool res = permutation(str,arr);
   if(res)
      cout << "Yes, the string can be formed by permutation of two other strings";
   else
      cout << "No, the string can't be formed by permutation of two other strings";
   return 0;
}

//including the required libraries
#include <bits/stdc++.h>
using namespace std;

// Function to sort the given string
// using counting sort
void countsort(string& str){

   //declaring the numbr of characters
   int numchar = 26;

   //string length
   int len = str.length();

   //initialise the count of array
   int count[numchar] = { 0 };

   //declaring an index param
   int idx = 0;

   //traversing the string
   for (int i = 0; i < len; i++) {
      char ch = str[i] ;
      count[ch - 'a']++;
   }

   //increasing order insertion
   for (int i = 0; i < numchar; i++) {
      int j = 0;
      for (j=0; j < count[i];j++) {
         str[idx] = i + 'a';
         idx++;
      }
   }
}

//check if string can be formed by permutations of two strings
bool permutation( string str,vector<string> arr){
   int size = arr.size();

   //sorting the given string
   countsort(str);

   //extracting two strings at a time
   for (int i = 0; i < size - 1; i++) {
      for (int j = i + 1; j < size; j++) {

         //concatenate the pair of string
         string concat = arr[i] + arr[j];

         // Sort the resultant string
         countsort(concat);

         //comparing if the order of characters in both strings are same
         if (concat.compare(str) == 0) {

            //if equal
            return true;
         }
      }
   }

   //no such combination exists
   return false;
}
int main(){

   //declaring the input string
   string str = "tutorials";

   //array of strings
   vector<string> arr{ "trils", "outa", "ginc", "abc" };
   printf("\nString 2:\n");
   for (int i = 0; i <4 ; i++){
      cout<<arr[i]<<endl;
   }
   bool res = permutation(str,arr);
   if(res)
      cout << "Yes, the string can be formed by permutation of two other strings";
   else
      cout << "No, the string can't be formed by permutation of two other strings";
   return 0;
}