Find the missing elements from 1 to M in given N ranges

Given N segments as ranges [L, R] where ranges are non-intersecting and non-overlapping. The task is to find all number between 1 to M that doesn’t belong to any of the given ranges.

Examples:

Input : N = 2, M = 6
        Ranges:
        [1, 2]
        [4, 5]
Output : 3, 6
Explanation: Only 3 and 6 are missing from
the above ranges.

Input : N = 1, M = 5
        Ranges:
        [2, 4]
Output : 1, 5

Approach: Given that we have N ranges, which are non-overlapping and non-intersecting. First of all, sort all segments based on starting value. After sorting, iterate from each segment and find the numbers which are missing.

Below is the implementation of the above approach:

C++

filter_none

edit
close

play_arrow

link
brightness_4
code

// C++ program to find mssing elements
// from given Ranges
  
#include <bits/stdc++.h>
using namespace std;
  
// Function to find mssing elements
// from given Ranges
void findMissingNumber(vector<pair<int, int> > ranges, int m)
{
    // First of all sort all the given ranges
    sort(ranges.begin(), ranges.end());
  
    // store ans in a different vector
    vector<int> ans;
  
    // prev is use to store end of
    // last range
    int prev = 0;
  
    // j is used as a counter for ranges
    for (int j = 0; j < ranges.size(); j++) {
        int start = ranges[j].first;
        int end = ranges[j].second;
  
        for (int i = prev + 1; i < start; i++)
            ans.push_back(i);
  
        prev = end;
    }
  
    // for last segment
    for (int i = prev + 1; i <= m; i++)
        ans.push_back(i);
  
    // finally print all answer
    for (int i = 0; i < ans.size(); i++) {
        if (ans[i] <= m)
            cout << ans[i] << " ";
    }
}
  
// Driver code
int main()
{
    int N = 2, M = 6;
  
    // Store ranges in vector of pair
    vector<pair<int, int> > ranges;
    ranges.push_back({ 1, 2 });
    ranges.push_back({ 4, 5 });
  
    findMissingNumber(ranges, M);
  
    return 0;
}

chevron_right






                        filter_none








                “”



Python3














                                    filter_none




                                    edit

                                    close




                                    play_arrow




                                    link

                                    brightness_4

                                    code
                                




















# Python3 program to find missing  


# elements from given Ranges  


  


# Function to find mssing elements  


# from given Ranges  


def findMissingNumber(ranges, m):  


  


    # First of all sort all the  


    # given ranges  


    ranges.sort()  


  


    # store ans in a different vector  


    ans = []  


  


    # prev is use to store end 


    # of last range 


    prev = 0


  


    # j is used as a counter for ranges  


    for j in range(len(ranges)):  


        start = ranges[j][0]  


        end = ranges[j][1]  


  


        for i in range(prev + 1, start):  


            ans.append(i)  


  


        prev = end  


  


    # for last segment  


    for i in range(prev + 1, m + 1):  


        ans.append(i)  


  


    # finally print all answer  


    for i in range(len(ans)):  


        if ans[i] <= m: 


            print(ans[i], end = " ")  


      


# Driver Code 


if __name__ == "__main__": 


      


    N, M = 2, 6


  


    # Store ranges in vector of pair  


    ranges = []  


    ranges.append([1, 2])  


    ranges.append([4, 5])  


  


    findMissingNumber(ranges, M)  


  


# This code is contributed  


# by Rituraj Jain 



















                        chevron_right







                        filter_none









PHP














                                    filter_none




                                    edit

                                    close




                                    play_arrow




                                    link

                                    brightness_4

                                    code
                                




















<?php 


// PHP program to find missing 


// elements from given Ranges 


  


// Function to find mssing elements 


// from given Ranges 


function findMissingNumber($ranges, $m) 


{ 


    // First of all sort all the 


    // given ranges 


    sort($ranges); 


      


    // store ans in a different vector 


    $ans = []; 


      


    // prev is use to store end 


    // of last range 


    $prev = 0; 


      


    // j is used as a counter for ranges 


    for ($j = 0; $j < count($ranges); $j++)  


    { 


        $start = $ranges[$j][0]; 


        $end = $ranges[$j][1]; 


      


        for ($i = $prev + 1; $i < $start; $i++)  


            array_push($ans, $i); 


              


        $prev = $end; 


    } 


      


    // for last segment 


    for ($i = $prev + 1; $i < $m + 1; $i++) 


            array_push($ans, $i); 


      


    // finally print all answer 


    for ($i = 0; $i < count($ans); $i++)  


    { 


        if ($ans[$i] <= $m) 


            echo "$ans[$i] "; 


    } 


} 


  


// Driver Code 


$N = 2; 


$M = 6; 


  


// Store ranges in vector of pair 


$ranges = []; 


array_push($ranges, [1, 2]); 


array_push($ranges, [4, 5]); 


  


findMissingNumber($ranges, $M) 


  


// This code is contributed 


// by Srathore 


?> 



















                        chevron_right







                        filter_none











Output:


3 6





competitive-programming-img





    

        My Personal Notes
        arrow_drop_up
    

    

        
        

            
            
        

    


Recommended Posts:
sahilshelangia
Check out this Author's contributed articles.
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please Improve this article if you find anything incorrect by clicking on  the "Improve Article" button below.