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C++ Function Miscellaneous

Precision of floating point numbers Using these functions floor(), ceil(), trunc(), round() and setprecision() in C++ function overloading in C++ Add two numbers using the function in C++ Advantage and disadvantage friend function C++ ATM machine program in C++ using functions Returning Multiple Values from a function using Tuple and Pair in C++ Find the Size of Array in C/C++ without using sizeof() function Pure Virtual function in C++ With Example Program Returning a function Pointer from a function in C/C++ Passing a Vector to a function in C++ functions in C++ With Types and Examples C++ Macro function Example Using Default Arguments with Virtual functions Virtual functions and Runtime Polymorphism Fesetround() and Fegetround() in C++ and their application Object as function Argument in C++ Private Member function in C++ Function Overriding in C++ C++ Program for Addition of Two Numbers Using functions function Object in C++ Elements of User Defined function in C++ Inline Functions in C++ Virtual Function in C++

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C++ Operators

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C++ Examples

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C++ Differences

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How To

How to concatenate two strings in C++ How to Reverse a String in C++ using Do-While Loop How to Reverse a String in C++ using for Loop How to Reverse a String in C++ using While Loop How to create a table in C++ How to Setup Environment for C++ Programming on Mac How to call a void function in C++ How to create a directory or folder in C/C++ How to create a library in C++ How to create a stack in C++ How to create the Processes with fork in C++ How to Handle Divide by Zero Exception in C++ How to Declare Unordered Sets in C++ How to Sort an Array in C++ How to run program in turbo c++ How to Use Getline in C++ How is Multiset Implemented in C++ How to Build a Program in C++ How to Declare a 2d Array Dynamically in C++ How to create a button in C++ How the value is passed in C++ How to calculate size of string in C++ How to convert binary string to int in C++ How to convert string to float in C++ How to remove space from string in C++ How to use pair in C++ How to use the string find() in C++ How to Remove an Element From an Array in C++ How to Take Space Separated input in C++ How to Copy in Turbo C++ How to Use Pow in C++ How to Use Set in C++ How to Create Singleton Class in C++ How to Allocate Memory Dynamically in C++ How to Close Turbo C++ in Windows 10 How to Use Modulus in C++

C++ Questions

What does Buffer Flush mean in C++ What is endl in C++ What is Unary Operator Overloading in C++ Which operators cannot be overloaded in C++ What is Static Member function in C++ What is This Pointer in C++ What is Upcasting in C++ What Kind of Exceptions Are Available in C++ What is Memory Allocation for Objects in C++ What is a Linked List in C++ is assignment operator inherited in C++ When should we write own Assignment operator in C++ What is an Object in C++ What is Copy Constructor in C++ What is a Static Member Function in C++

C++ Interview Questions

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Miscellaneous

External merge sort in C++ Remove duplicates from sorted array in C++ C++ References C++ Mutable keyword initialize Array of objects with parameterized constructors in C++ Storage Classes in C goto statement in C and C++ C++ String Concatenation Heap Sort in C++ Swap numbers in C++ input Iterators in C++ Fibonacci Series in C++ Stack in C++ Maps in C++ Queue in C++ C++ Bitset C++ Algorithms Priority Queue in C++ C++ Multimap C++ Deque C++ array of Pointers Timsort Implementation Using C++ CPP Templates C++ Aggregation C++ Enumeration C++ Object Class C++ Queue initialize Vector in C++ Vector in C++ C++ STL Components C++ Maximum index Problem C++ find missing in the second array C++ Namespaces C++ OOPs Concept C++ Static C++ Structs C++ Try-Catch C++ User Defined Exceptions C++ Virtual Destructor Snake Code in C++ Splitting a string in C++ C++ Bidirectional Iterators C++ forward Iterators C++ Iterators C++ Output Iterators C++ Range-based for Loop Converting string into integer in C++ 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C++ Program to find the largest number formed from an array

Given an array, write a program to find the largest number that will be formed from the elements of the array. Arrangement should be done in such a way that all the elements contribute to make the largest number. Also, return the largest formed number in string format because the number can be very large.

For example

Test case 1

N = 5

Arr[] = {5, 9, 30, 3, 34}

Output = 9534330

Explanation

The largest value formed with the arrangement of 9,5,34,3,30.

Test case 2

N = 4

Arr[] = {60, 546, 548, 54}

Output = 6054854654

Explanation

The largest value formed with the arrangement of 60,548,546,54.

Brute-force approach

A simple approach is to sort the array and form a string in order to make a largest number. The array sorted in descending order using bubble sort does not work here.

For example, if we take 548, it is greater than 60 but after sorting 60 comes before.

Similarly, 98 is greater than 9 but after sorting it comes after.

Below is the code implementation.

Code

#include <algorithm>

#include <iostream>

#include <string>

#include <vector>

#include<bits/stdc++.h>

using namespace std;


string number(vector<int>& nums){ // declare a function

  if( nums[0]==0 && nums[nums.size()-1] == 0) // if array contains 0

return "0";

        vector<string> result;

          // push array element to string vector

        for(auto x:nums){

            result.push_back(to_string(x));

        }

          // Sort the result vector

        for(int i=0;i<nums.size()-1;i++){

            for(int j=0;j<nums.size()-i-1;j++){

                if(result[j]+result[j+1]<result[j+1]+result[j]){

                    swap(result[j],result[j+1]);

                }

            }

        }

          // Append it to ans string

        string ans="";

        for(int i=0;i<result.size();i++){

            ans+=result[i];

        }

        return ans; // print ans

}

int main()

{

          vector<int> arr;

          arr.push_back(54);

          arr.push_back(546);

          arr.push_back(548);

          arr.push_back(60);

cout  << number(arr);

          return 0;

}

Output

6054854654

Time complexity

O(n*n)

Space complexity

O(1)

Comparison based sorting

The problem occurred in the brute force approach will be covered in this approach. While sorting the array, we will modify the default compare function according to our needs.

The function my_compare() will work in this way.

This function will compare two numbers X and Y. If the formation of XY is greater then X will come first in the sorting order otherwise Y will come in the sorting order.

For example, if we have x as 541 and Y as 60. We compare 54160 and 60541. The greater one is 60541 so Y remains first.

Code

#include <algorithm>

#include <iostream>

#include <string>

#include <vector>

#include<bits/stdc++.h>

using namespace std;


int my_Compare(int X, int Y)

{

string x1= to_string(X); // x is  convert to string

    string y1 =to_string(Y); // y is  convert to string

         

          string XY = x1.append(y1); // Make combination of XY by append X to Y


          string YX = y1.append(x1); // Make combination of YX by append Y to X

     

          return XY.compare(YX) > 0 ? 1 : 0; // Compare for the greater one

}


void printLargest(vector<int> arr)

{
       

          sort(arr.begin(), arr.end(), my_Compare); // Sort the arr by using my_Compare

          for (int i = 0; i < arr.size(); i++)

                   cout << arr[i]; // Print the array arranged in form of largest number

}

int main()

{

          vector<int> arr; // make a vector

          arr.push_back(54);

          arr.push_back(546);

          arr.push_back(548);

          arr.push_back(60);

          printLargest(arr);

        return 0;

}

Output

6054854654

Time complexity

O(nlogn)

Space complexity

O(n)

Using itertools

If we want to do this problem using Python, a module itertools.combination() is used to find all the combinations of an array.

For example

Input : arr[] = [1, 2, 3, 4],

            r = 2

Output : [[1, 2], [1, 3], [1, 4], [2, 3], [2, 4], [3, 4]]

Here r is the length of a set of sequences that can be formed.

Now this module can be applied to our array. We can find all the possible combinations of the array and make a string of a particular sequence set.

Finally, we will get the largest string.

Code

#import itertools from permutations

from itertools import permutations

def largest(l): # function to print largest number formed

    lst = [] #an array to store the result

    for i in permutations(l, len(l)):

        # provides all permutations of the list values,

        # store them in list to find max

        lst.append("".join(map(str,i)))

    return max(lst) # return max of the lst

print(largest([54, 546, 548, 60])) # Call largest function

Output

6054854654