Find elements which are present in first array and not in second (original) (raw)

Given two arrays, the task is that we find numbers which are present in first array, but not present in the second array.

**Examples :

Input : a[] = {1, 2, 3, 4, 5, 10};
b[] = {2, 3, 1, 0, 5};
Output : 4 10
4 and 10 are present in first array, but
not in second array.
Input : a[] = {4, 3, 5, 9, 11};
b[] = {4, 9, 3, 11, 10};
Output : 5

**Method 1 (Simple): A Naive Approach is to use two loops and check element which not present in second array.

**Implementation:

C++ `

// C++ simple program to // find elements which are // not present in second array #include<bits/stdc++.h> using namespace std;

// Function for finding // elements which are there // in a[] but not in b[]. void findMissing(int a[], int b[], int n, int m) { for (int i = 0; i < n; i++) { int j; for (j = 0; j < m; j++) if (a[i] == b[j]) break;

    if (j == m)
        cout << a[i] << " ";
}

}

// Driver code int main() { int a[] = { 1, 2, 6, 3, 4, 5 }; int b[] = { 2, 4, 3, 1, 0 }; int n = sizeof(a) / sizeof(a[0]); int m = sizeof(b) / sizeof(b[1]); findMissing(a, b, n, m); return 0; }

Java

// Java simple program to // find elements which are // not present in second array class GFG {

// Function for finding elements 
// which are there in a[] but not
// in b[].
static void findMissing(int a[], int b[], 
                        int n, int m)
{
    for (int i = 0; i < n; i++)
    {
        int j;
        
        for (j = 0; j < m; j++)
            if (a[i] == b[j])
                break;

        if (j == m)
            System.out.print(a[i] + " ");
    }
}

// Driver Code
public static void main(String[] args)
{
    int a[] = { 1, 2, 6, 3, 4, 5 };
    int b[] = { 2, 4, 3, 1, 0 };
    
    int n = a.length;
    int m = b.length;
    
    findMissing(a, b, n, m);
}

}

// This code is contributed // by Anant Agarwal.

Python 3

Python 3 simple program to find elements

which are not present in second array

Function for finding elements which

are there in a[] but not in b[].

def findMissing(a, b, n, m):

for i in range(n):
    for j in range(m):
        if (a[i] == b[j]):
            break

    if (j == m - 1):
        print(a[i], end = " ")

Driver code

if name == "main":

a = [ 1, 2, 6, 3, 4, 5 ]
b = [ 2, 4, 3, 1, 0 ]
n = len(a)
m = len(b)
findMissing(a, b, n, m)

This code is contributed

by ChitraNayal

C#

// C# simple program to find elements // which are not present in second array using System;

class GFG {

// Function for finding elements 
// which are there in a[] but not
// in b[].
static void findMissing(int []a, int []b, 
                        int n, int m)
{
    for (int i = 0; i < n; i++)
    {
        int j;
        
        for (j = 0; j < m; j++)
            if (a[i] == b[j])
                break;

        if (j == m)
            Console.Write(a[i] + " ");
    }
}

// Driver code
public static void Main()
{
    int []a = {1, 2, 6, 3, 4, 5};
    int []b = {2, 4, 3, 1, 0};
    
    int n = a.Length;
    int m = b.Length;
    
    findMissing(a, b, n, m);
}

}

// This code is contributed by vt_m.

JavaScript

PHP

a,a, a,b, n,n, n,m) { for ( i=0;i = 0; i=0;i < n;n; n;i++) { $j; for ($j = 0; j<j < j<m; $j++) if ($a[$i] == b[b[b[j]) break; if ($j == $m) echo a[a[a[i] , " "; } } // Driver code $a = array( 1, 2, 6, 3, 4, 5 ); $b = array( 2, 4, 3, 1, 0 ); n=count(n = count(n=count(a); m=count(m = count(m=count(b); findMissing($a, b,b, b,n, $m); // This code is contributed by anuj_67. ?>

`

**Time complexity: **O(n*m) since using inner and outer loops
**Auxiliary Space : O(1)

**Method 2 (Use Hashing): In this method, we store all elements of second array in a hash table (unordered_set). One by one check all elements of first array and print all those elements which are not present in the hash table.

**Implementation:

C++ `

// C++ efficient program to // find elements which are not // present in second array #include<bits/stdc++.h> using namespace std;

// Function for finding // elements which are there // in a[] but not in b[]. void findMissing(int a[], int b[], int n, int m) { // Store all elements of // second array in a hash table unordered_set s; for (int i = 0; i < m; i++) s.insert(b[i]);

// Print all elements of
// first array that are not
// present in hash table
for (int i = 0; i < n; i++)
    if (s.find(a[i]) == s.end())
        cout << a[i] << " ";

}

// Driver code int main() { int a[] = { 1, 2, 6, 3, 4, 5 }; int b[] = { 2, 4, 3, 1, 0 }; int n = sizeof(a) / sizeof(a[0]); int m = sizeof(b) / sizeof(b[1]); findMissing(a, b, n, m); return 0; }

Java

// Java efficient program to find elements // which are not present in second array import java.util.HashSet; import java.util.Set;

public class GfG{

// Function for finding elements which
// are there in a[] but not in b[].
static void findMissing(int a[], int b[],
                int n, int m)
{
    // Store all elements of
    // second array in a hash table
    HashSet<Integer> s = new HashSet<>();
    for (int i = 0; i < m; i++)
        s.add(b[i]);
    
    // Print all elements of first array
    // that are not present in hash table
    for (int i = 0; i < n; i++)
        if (!s.contains(a[i]))
            System.out.print(a[i] + " ");
}

public static void main(String []args){
    
    int a[] = { 1, 2, 6, 3, 4, 5 };
    int b[] = { 2, 4, 3, 1, 0 };
    int n = a.length;
    int m = b.length;
    findMissing(a, b, n, m);
}

}

// This code is contributed by Rituraj Jain

Python3

Python3 efficient program to find elements

which are not present in second array

Function for finding elements which

are there in a[] but not in b[].

def findMissing(a, b, n, m):

# Store all elements of second 
# array in a hash table
s = dict()
for i in range(m):
    s[b[i]] = 1

# Print all elements of first array 
# that are not present in hash table
for i in range(n):
    if a[i] not in s.keys():
        print(a[i], end = " ")

Driver code

a = [ 1, 2, 6, 3, 4, 5 ] b = [ 2, 4, 3, 1, 0 ] n = len(a) m = len(b) findMissing(a, b, n, m)

This code is contributed by mohit kumar

C#

// C# efficient program to find elements // which are not present in second array using System; using System.Collections.Generic;

class GfG {

// Function for finding elements which 
// are there in a[] but not in b[]. 
static void findMissing(int []a, int []b, 
                int n, int m) 
{ 
    // Store all elements of 
    // second array in a hash table 
    HashSet<int> s = new HashSet<int>(); 
    for (int i = 0; i < m; i++) 
        s.Add(b[i]); 
    
    // Print all elements of first array 
    // that are not present in hash table 
    for (int i = 0; i < n; i++) 
        if (!s.Contains(a[i]))
            Console.Write(a[i] + " "); 
} 

// Driver code
public static void Main(String []args)
{
    int []a = { 1, 2, 6, 3, 4, 5 }; 
    int []b = { 2, 4, 3, 1, 0 }; 
    int n = a.Length; 
    int m = b.Length; 
    findMissing(a, b, n, m);
}

}

/* This code contributed by PrinciRaj1992 */

JavaScript

`

**Time complexity : O(n+m)
**Auxiliary Space : O(n)

Approach 3: Recursion

Algorithm:

  1. ****"findMissing"** function takes four parameters, array ****"a"** of size ****"n"** and array ****"b"** of size ****"m".**
  2. **Base case : If **n==0 , then there are no more elements left to check, so return from the function.
  3. **Recursive case : Check if the first element of array ****"a"** is present in array ****"b".** For this, use a **for loop and iterate over all elements of array ****"b"**.
  4. If first element of array ****"a"** is not in array ****"b"**, print it.
  5. Recursively call the ****"findMissing"** function with the remaining elements of array ****"a"** and array ****"b"**. For this, increment the pointer of array ****"a"** and decrease it's size ****"n"** by **1.
  6. Call the recursive function ****"findMissing"** in main() with array ****"a"** and array ****"b"**, and their respective sizes ****"n"** and ****"m"**.

Here's the implementation:

C++ `

#include using namespace std;

void findMissing(int a[], int b[], int n, int m) { // Base case: if n is zero, then there are no more elements to check if (n == 0) { return; }

// Recursive case: check if the first element of a[] is in b[]
int i;
for (i = 0; i < m; i++) {
    if (a[0] == b[i]) {
        break;
    }
}

// If the first element of a[] is not in b[], print it
if (i == m) {
    cout << a[0] << " ";
}

// Recursively call findMissing with the remaining elements of a[] and b[]
findMissing(a+1, b, n-1, m);

}

int main() { int a[] = { 1, 2, 6, 3, 4, 5 }; int b[] = { 2, 4, 3, 1, 0 }; int n = sizeof(a) / sizeof(a[0]); int m = sizeof(b) / sizeof(b[1]);

findMissing(a, b, n, m);
cout << endl;

return 0;

}

// This code is contributed by Vaibhav Saroj

C

#include <stdio.h>

void findMissing(int a[], int b[], int n, int m) { // Base case: if n is zero, then there are no more elements to check if (n == 0) { return; }

// Recursive case: check if the first element of a[] is in b[]
int i;
for (i = 0; i < m; i++) {
    if (a[0] == b[i]) {
        break;
    }
}

// If the first element of a[] is not in b[], print it
if (i == m) {
    printf("%d ", a[0]);
}

// Recursively call findMissing with the remaining elements of a[] and b[]
findMissing(a+1, b, n-1, m);

}

int main() { int a[] = { 1, 2, 6, 3, 4, 5 }; int b[] = { 2, 4, 3, 1, 0 }; int n = sizeof(a) / sizeof(a[0]); int m = sizeof(b) / sizeof(b[0]);

findMissing(a, b, n, m);
printf("\n");

return 0;

}

// This code is contributed by Vaibhav Saroj

Java

import java.util.*;

class Main { public static void findMissing(int[] a, int[] b, int n, int m) { // Base case: if n is zero, then there are no more elements to check if (n == 0) { return; }

    // Recursive case: check if the first element of a[] is in b[]
    int i;
    for (i = 0; i < m; i++) {
        if (a[0] == b[i]) {
            break;
        }
    }

    // If the first element of a[] is not in b[], print it
    if (i == m) {
        System.out.print(a[0] + " ");
    }

    // Recursively call findMissing with the remaining elements of a[] and b[]
    findMissing(Arrays.copyOfRange(a, 1, n), b, n-1, m);
}

public static void main(String[] args) {
    int[] a = { 1, 2, 6, 3, 4, 5 };
    int[] b = { 2, 4, 3, 1, 0 };
    int n = a.length;
    int m = b.length;

    findMissing(a, b, n, m);
    System.out.println();
}

}

// This code is contributed by Vaibhav Saroj

Python3

code

def find_missing(a, b, n, m): # Base case: if n is zero, then there are no more elements to check if n == 0: return

# Recursive case: check if the first element of a[] is in b[]
i = 0
while i < m:
    if a[0] == b[i]:
        break
    i += 1

# If the first element of a[] is not in b[], print it
if i == m:
    print(a[0], end=" ")

# Recursively call find_missing with the remaining elements of a[] and b[]
find_missing(a[1:], b, n - 1, m)

def main(): a = [1, 2, 6, 3, 4, 5] b = [2, 4, 3, 1, 0] n = len(a) m = len(b)

find_missing(a, b, n, m)
print()

if name == "main": main()

#This code is contributed by aeroabrar_31

C#

using System;

public class Program { public static void FindMissing(int[] a, int[] b, int n, int m) { // Base case: if n is zero, then there are no more elements to check if (n == 0) { return; }

    // Recursive case: check if the first element of a[] is in b[]
    int i;
    for (i = 0; i < m; i++)
    {
        if (a[0] == b[i])
        {
            break;
        }
    }

    // If the first element of a[] is not in b[], print it
    if (i == m)
    {
        Console.Write(a[0] + " ");
    }

    // Recursively call FindMissing with the remaining elements of a[] and b[]
    FindMissing(new ArraySegment<int>(a, 1, n - 1).ToArray(), b, n - 1, m);
}

public static void Main(string[] args)
{
    int[] a = { 1, 2, 6, 3, 4, 5 };
    int[] b = { 2, 4, 3, 1, 0 };
    int n = a.Length;
    int m = b.Length;

    FindMissing(a, b, n, m);
    Console.WriteLine();
}

} //This code is contributed by aeroabrar_31

JavaScript

function findMissing(a, b, n, m) { // Base case: if n is zero, then there are no more elements to check if (n === 0) { return; }

// Recursive case: check if the first element of a[] is in b[] let i; for (i = 0; i < m; i++) { if (a[0] === b[i]) { break; } }

// If the first element of a[] is not in b[], print it if (i === m) { console.log(a[0] + " "); }

// Recursively call findMissing with the remaining elements of a[] and b[] findMissing(a.slice(1), b, n - 1, m); }

const a = [1, 2, 6, 3, 4, 5]; const b = [2, 4, 3, 1, 0]; const n = a.length; const m = b.length;

findMissing(a, b, n, m); console.log(); // add a newline at the end

// This code is contributed by Vaibhav Saroj

`

This Recursive approach and code is contributed by Vaibhav Saroj .

**The time and space complexity:

Time complexity : O(nm) .

Space complexity : O(1) .