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Sort a stream of integers
  • Last Updated : 08 Mar, 2021

Given an array, arr[] of size N whose elements from left to right, must be read as an incoming stream of integers, the task is to sort the stream of integers and print accordingly.

Examples:

Input: arr[] = {2, 4, 1, 7, 3}
Output: 1 2 3 4 7
Explanation: 
First element in the stream: 2 → Sorted list: {2}
Second element in the stream: 4 → Sorted list: {2, 4}
Third element in the stream: 1 → Sorted list: {1, 2, 4}
Fourth element in the stream: 7 → Sorted list: {1, 2, 4, 7}
Fifth element in the stream: 3 → Sorted list: {1, 2, 3, 4, 7}

Input: arr[] = {4, 1, 7, 6, 2}
Output: 1 2 4 6 7
Explanation:
First element in the stream: 4 → Sorted list: {4}
Second element in the stream: 1 → Sorted list: {1, 4}
Third element in the stream: 7 → Sorted list: {1, 4, 7}
Fourth element in the stream: 6 → Sorted list: {1, 4, 6, 7}
Fifth element in the stream: 2 → Sorted list: {1, 2, 4, 6, 7}

Naive Approach: The simplest approach is to <a href=”https://www.geeksforgeeks.org/c-program-to-traverse-an-array/”>traverse the array and for each array element, linearly scan the array and find the right position of that element and place it in the array.



Below is the implementation of the above approach:

C++




// C++ program for the above approach
#include <bits/stdc++.h>
using namespace std;
 
// Function to sort a stream of integers
void Sort(vector<int>& ans, int num)
{
    // Stores the position of
    // array elements
    int pos = -1;
 
    // Traverse through the array
    for (int i = 0; i < ans.size(); i++) {
 
        // If any element is found to be
        // greater than the current element
        if (ans[i] >= num) {
            pos = i;
            break;
        }
    }
 
    // If an element > num is not present
    if (pos == -1)
        ans.push_back(num);
 
    // Otherwise, place the number
    // at its right position
    else
        ans.insert(ans.begin() + pos, num);
}
 
// Function to print the sorted stream of integers
void sortStream(int arr[], int N)
{
    // Stores the sorted stream of integers
    vector<int> ans;
 
    // Traverse the array
    for (int i = 0; i < N; i++) {
 
        // Function Call
        Sort(ans, arr[i]);
 
        // Print the array after
        // every insertion
        for (int i = 0; i < ans.size(); i++) {
            cout << ans[i] << " ";
        }
        cout << endl;
    }
}
 
// Driver Code
int main()
{
    int arr[] = { 4, 1, 7, 6, 2 };
    int N = sizeof(arr) / sizeof(arr[0]);
 
    sortStream(arr, N);
 
    return 0;
}

Java




// Java program for the above approach
import java.util.*;
 
class GFG{
 
// Function to sort a stream of integers
static void Sort(Vector<Integer> ans, int num)
{
     
    // Stores the position of
    // array elements
    int pos = -1;
 
    // Traverse through the array
    for(int i = 0; i < ans.size(); i++)
    {
         
        // If any element is found to be
        // greater than the current element
        if (ans.get(i) >= num)
        {
            pos = i;
            break;
        }
    }
 
    // If an element > num is not present
    if (pos == -1)
        ans.add(num);
 
    // Otherwise, place the number
    // at its right position
    else
        ans.add(pos, num);
}
 
// Function to print the sorted stream of integers
static void sortStream(int arr[], int N)
{
     
    // Stores the sorted stream of integers
    Vector<Integer> ans = new Vector<Integer>();
 
    // Traverse the array
    for(int i = 0; i < N; i++)
    {
         
        // Function Call
        Sort(ans, arr[i]);
 
        // Print the array after
        // every insertion
        for(int j = 0; j < ans.size(); j++)
        {
            System.out.print(ans.get(j) + " ");
        }
        System.out.println();
    }
}
 
// Driver Code
public static void main(String[] args)
{
    int arr[] = { 4, 1, 7, 6, 2 };
    int N = arr.length;
 
    sortStream(arr, N);
}
}
 
// This code is contributed by Amit Katiyar

Python3




# Python program for the above approach
 
# Function to sort a stream of integers
def Sort(ans, num):
   
    # Stores the position of
    # array elements
    pos = -1;
 
    # Traverse through the array
    for  i in range(len(ans)):
 
        # If any element is found to be
        # greater than the current element
        if (ans[i] >= num):
            pos = i;
            break;
 
    # If an element > num is not present
    if (pos == -1):
        ans.append(num);
 
    # Otherwise, place the number
    # at its right position
    else:
        ans.insert(pos,num);
    return ans;
 
# Function to print the sorted stream of integers
def sortStream(arr, N):
   
    # Stores the sorted stream of integers
    ans = list();
 
    # Traverse the array
    for i in range(N):
 
        # Function Call
        ans = Sort(ans, arr[i]);
 
        # Print the array after
        # every insertion
        for j in range(len(ans)):
            print(ans[j], end = " ");
 
        print();
 
# Driver Code
if __name__ == '__main__':
    arr = [4, 1, 7, 6, 2];
    N = len(arr);
 
    sortStream(arr, N);
 
# This code is contributed by 29AjayKumar

C#




// C# program for the above approach
using System;
using System.Collections.Generic;
class GFG{
 
// Function to sort a stream of integers
static void Sort(List<int> ans, int num)
{
     
    // Stores the position of
    // array elements
    int pos = -1;
 
    // Traverse through the array
    for(int i = 0; i < ans.Count; i++)
    {
         
        // If any element is found to be
        // greater than the current element
        if (ans[i] >= num)
        {
            pos = i;
            break;
        }
    }
 
    // If an element > num is not present
    if (pos == -1)
        ans.Add(num);
 
    // Otherwise, place the number
    // at its right position
    else
        ans.Insert(pos, num);
}
 
// Function to print the sorted stream of integers
static void sortStream(int []arr, int N)
{
     
    // Stores the sorted stream of integers
    List<int> ans = new List<int>();
 
    // Traverse the array
    for(int i = 0; i < N; i++)
    {
         
        // Function Call
        Sort(ans, arr[i]);
 
        // Print the array after
        // every insertion
        for(int j = 0; j < ans.Count; j++)
        {
            Console.Write(ans[j] + " ");
        }
        Console.WriteLine();
    }
}
 
// Driver Code
public static void Main(String[] args)
{
    int []arr = { 4, 1, 7, 6, 2 };
    int N = arr.Length;
    sortStream(arr, N);
}
}
 
// This code is contributed by 29AjayKumar
Output: 
4 
1 4 
1 4 7 
1 4 6 7 
1 2 4 6 7

 

Time Complexity: O(N2)
Auxiliary Space: O(N)

Efficient Approach: To optimize the above approach, the idea is to use a Binary Search to find the correct position of each element in the sorted list. Follow the steps below to solve the problem:

  • Initialize an array ans[] to store the final sorted stream of numbers.
  • Traverse the array arr[] as a stream of numbers using a variable i and perform the following steps:
    • If array ans is empty, push arr[i] to ans.
    • Otherwise, find the correct position of arr[i] in the already sorted array ans[] using lower_bound() and push arr[i] at its correct position.
  • After completing the above steps, print the array ans[].

Below is the implementation of the above approach:

C++




// C++ program for the above approach
#include <bits/stdc++.h>
using namespace std;
 
// Function to sort a stream of integers
void Sort(vector<int>& ans, int num)
{
    // If the element is greater than
    // all the elements in the sorted
    // array, then it push at the back
    if (lower_bound(ans.begin(),
                    ans.end(), num)
        == ans.end()) {
        ans.push_back(num);
    }
 
    // Otherwise, find its correct position
    else {
        int pos = lower_bound(ans.begin(),
                              ans.end(),
                              num)
                  - ans.begin();
 
        // Insert the element
        ans.insert(ans.begin() + pos,
                   num);
    }
}
 
// Function to print the sorted stream of integers
void sortStream(int arr[], int N)
{
    // Stores the sorted stream of integers
    vector<int> ans;
 
    // Traverse the array
    for (int i = 0; i < N; i++) {
 
        // Function Call
        Sort(ans, arr[i]);
 
        // Print the array after
        // every insertion
        for (int i = 0; i < ans.size(); i++) {
            cout << ans[i] << " ";
        }
        cout << endl;
    }
}
 
// Driver Code
int main()
{
    int arr[] = { 4, 1, 7, 6, 2 };
    int N = sizeof(arr) / sizeof(arr[0]);
 
    sortStream(arr, N);
 
    return 0;
}
Output: 
4 
1 4 
1 4 7 
1 4 6 7 
1 2 4 6 7

 

Time Complexity: O(N*log N)
Auxiliary Space: O(N)

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