Question

• Take an unknown number of integers as input and print the second smallest number.
• If there is no second smallest number in the sequence the program should print an error message and quit.
• Write a function that takes a vector as argument and that returns an int containing the second smallest number. If no such number exists, the function should throw an exception that in turn is caught in main.
• Your program should compute its answer with a complexity no worse than O ( n ). Note that this requirement excludes, e.g., sorting the sequence of numbers.
  • The professor means to say: "Your program should compute its answer with a complexity no worse than O ( n ). Note that this requirement excludes, e.g., the use of sorting algorithms on the sequence of numbers."
• The program should read integers from cin until something non-numeric is entered.

Two examples of a correct execution of the program are shown below:

Enter the numbers in random order: (close by entering q)
34 254 1 -5 -13 q
The second smallest number is -5 

And:

Enter the numbers in random order: (close by entering q)
4 4 4 4 4 q
error: no second smallest

Code using c++ only.

Answer 1

here is code:

#include <iostream>
#include <sstream>
#include <vector>
#include <algorithm>
using namespace std;

int secondSmallestNumber(vector<int> &v); // function declaration

// main function to run program
int main() {
   // prompt user to enter input data
   cout << "Enter the numbers in random order: (close by entering q)" << endl;
   vector<int> v; // create a int vector object to pass it as function parameter to secondSmallestNumber function
   int input; // declare variable to store use input
   stringstream ss; // create stringstream object to convert string in to integers
   string str; // variable to store user input as string
   bool flag = false; // create flag to indicate noninteger value is encountered
   while (!flag) {
       getline(cin, str); // get string input from user
       ss.clear(); // clear the stringstream for second input
       ss << str; // pass string to stringstream object
       while (ss >> input || !ss.eof()) {
           //while loop to continue till error occurs converting integers of end of stream occurs;
           //check if error ouccurs in parsing
           if (ss.fail()) {
               flag = true; // set flaf to true
               break; // break the inner while loop
           }
           v.push_back(input); // add integer to end of vector
       }//end of inner while loop
   }//end of outer while loop
   int result; // variable to store secondsmallest number
   //try getting result value from seconsmallestnumber function
   //if exception is thrown, print error message
   try {
       result = secondSmallestNumber(v);
       cout << "The second smallest number is " << result << endl; // print result
   }
   catch (const exception& e) {
       cout << "error: no second smallest" << endl;
   }

   return 0;
}

// function implimentation
int secondSmallestNumber(vector<int> &v) throw(...){
   //sort the vector ,complexity is exluded for sorting algorithms
   std::sort(v.begin(), v.end());
   int number = v.at(0); // get first element in vector as smallest number
   //loop the vector for second smallest number
   for (int i = 0; i < v.size() - 1; i++) {
       // check for second smallest number
       if (v.at(i + 1) > number) { // comparing i+1 as the first element is already taken for comprison
           // if number found return the number
           return v.at(i + 1);
       }
   }
   // if number not found then throw exception
   throw exception("error");
   //this is linear search so worst case complexity is number not found
   //eg. O(n);
}