Check if two arrays are equal or not (original) (raw)

Last Updated : 26 Dec, 2024

Given two arrays, **a and **b of equal length. The task is to determine if the given arrays are equal or not. Two arrays are considered equal if:

Both arrays contain the same set of elements.
The arrangements (or permutations) of elements may be different.
If there are repeated elements, the counts of each element must be the same in both arrays.

**Examples:

**Input: a[] = [1, 2, 5, 4, 0], b[] = [2, 4, 5, 0, 1]
**Output: true

**Input: a[] = [1, 2, 5, 4, 0, 2, 1], b[] = [2, 4, 5, 0, 1, 1, 2]
**Output: true

**Input: a[] = [1, 7, 1], b[] = [7, 7, 1]
**Output: false

Table of Content

[Naive Approach] Using Sorting - O(n*log n) Time and O(1) Space
[Expected Approach] Using Hashing - O(n) Time and O(n) Space

[Naive Approach] Using Sorting - O(n*log n) Time and O(1) **Space

The basic idea is to **sort the both arrays. Compare the arrays element by element one by one if all are same then it is equal array otherwise it is not.

C++ `

// C++ program to find given two array // are equal or not #include <bits/stdc++.h> using namespace std;

bool checkEqual(vector& a, vector& b) { int n = a.size(), m = b.size();

// If lengths of array are not equal means
// array are not equal
if (n != m) return false;
sort(a.begin(), a.end());
sort(b.begin(), b.end());
for (int i = 0; i < n; i++)
    if (a[i] != b[i])
        return false;

// If all elements were same.
return true;

}

int main() { vector a = { 3, 5, 2, 5, 2 }; vector b = { 2, 3, 5, 5, 2 };

if (checkEqual(a, b))
    cout << "true";
else
    cout << "false";
return 0;

}

Java

import java.util.Arrays;

class GfG { static boolean checkEqual(int[] a, int[] b) {

    // If lengths of array are not equal means
    // array are not equal
    if (a.length != b.length) return false;
    Arrays.sort(a);
    Arrays.sort(b);
    for (int i = 0; i < a.length; i++)
        if (a[i] != b[i])
            return false;

    // If all elements were same.
    return true;
}

public static void main(String[] args) {
    int[] a = { 3, 5, 2, 5, 2 };
    int[] b = { 2, 3, 5, 5, 2 };
    if (checkEqual(a, b))
        System.out.println("true");
    else
        System.out.println("false");
}

}

Python

def checkEqual(a, b):

# If lengths of array are not equal means
# array are not equal
if len(a) != len(b):
    return False
return sorted(a) == sorted(b)

if name == 'main': a = [3, 5, 2, 5, 2] b = [2, 3, 5, 5, 2]

if checkEqual(a, b):
    print("true")
else:
    print("false")

C#

using System; using System.Linq;

class GfG { static bool CheckEqual(int[] a, int[] b) {

    // If lengths of array are not equal means
    // array are not equal
    if (a.Length != b.Length) return false;
    Array.Sort(a);
    Array.Sort(b);
    for (int i = 0; i < a.Length; i++)
        if (a[i] != b[i])
            return false;

    // If all elements were same.
    return true;
}

static void Main() {
    int[] a = { 3, 5, 2, 5, 2 };
    int[] b = { 2, 3, 5, 5, 2 };

    if (CheckEqual(a, b))
        Console.WriteLine("true");
    else
        Console.WriteLine("false");
}

}

JavaScript

function checkEqual(a, b) { // If lengths of array are not equal means // array are not equal if (a.length !== b.length) return false; a.sort(); b.sort(); for (let i = 0; i < a.length; i++) if (a[i] !== b[i]) return false;

// If all elements were same.
return true;

}

//Driver Code const a = [3, 5, 2, 5, 2]; const b = [2, 3, 5, 5, 2]; console.log(checkEqual(a, b) ? 'true' : 'false');

**Time Complexity: O(n*log n), since sorting is used
**Auxiliary Space: O(1)

[Expected Approach] UsingHashing- O(n) Time and O(n) Space

Use of a hash map to count the occurrences of each element in one array and then verifying these counts against the second array.

C++ `

#include #include #include using namespace std;

bool checkEqual(vector& a, vector& b) { int n = a.size(), m = b.size(); if (n != m) return false;

unordered_map<int, int> mp;
for (int i = 0; i < n; i++)
    mp[a[i]]++;

for (int i = 0; i < n; i++) {
    if (mp.find(b[i]) == mp.end())
        return false;

    if (mp[b[i]] == 0)
        return false;
  
    mp[b[i]]--;
}
return true;

}

int main() { vector a = { 3, 5, 2, 5, 2 }; vector b = { 2, 3, 5, 5, 2 };

if (checkEqual(a, b))
    cout << "true";
else
    cout << "false";
return 0;

}

Java

import java.io.; import java.util.;

class GfG {

public static boolean checkEqual(int a[], int b[]) {
    int n = a.length, m = b.length;
    if (n != m)
        return false;

    Map<Integer, Integer> map
        = new HashMap<Integer, Integer>();
    int count = 0;
    for (int i = 0; i < n; i++) {
        if (map.get(a[i]) == null)
            map.put(a[i], 1);
        else {
            count = map.get(a[i]);
            count++;
            map.put(a[i], count);
        }
    }

    for (int i = 0; i < n; i++) {

        if (!map.containsKey(b[i]))
            return false;

        if (map.get(b[i]) == 0)
            return false;

        count = map.get(b[i]);
        --count;
        map.put(b[i], count);
    }

    return true;
}

public static void main(String[] args) {
    int a[] = { 3, 5, 2, 5, 2 };
    int b[] = { 2, 3, 5, 5, 2 };

    if (checkEqual(a, b))
        System.out.println("true");
    else
        System.out.println("false");
}

}

Python

def checkEqual(a, b): n, m = len(a), len(b) if n != m: return False

mp = {}
for num in a:
    mp[num] = mp.get(num, 0) + 1

for num in b:
    if num not in mp:
        return False
    if mp[num] == 0:
        return False
    mp[num] -= 1
return True

if name == 'main': a = [3, 5, 2, 5, 2] b = [2, 3, 5, 5, 2]

if checkEqual(a, b):
    print("true")
else:
    print("false")

C#

using System; using System.Collections.Generic; using System.Linq;

class GfG { static bool CheckEqual(int[] a, int[] b) { int n = a.Length, m = b.Length; if (n != m) return false;

    var mp = new Dictionary<int, int>();
    foreach (var num in a) {
        if (mp.ContainsKey(num))
            mp[num]++;
        else
            mp[num] = 1;
    }

    foreach (var num in b) {
        if (!mp.ContainsKey(num) || mp[num] == 0)
            return false;
        mp[num]--;
    }
    return true;
}

static void Main() {
    int[] a = { 3, 5, 2, 5, 2 };
    int[] b = { 2, 3, 5, 5, 2 };

    Console.WriteLine(CheckEqual(a, b) ? "true" : "false");
}

}

JavaScript

function checkEqual(a, b) { const n = a.length, m = b.length; if (n !== m) return false;

const mp = {};
for (let num of a) {
    mp[num] = (mp[num] || 0) + 1;
}

for (let num of b) {
    if (!(num in mp) || mp[num] === 0)
        return false;
    mp[num]--;
}
return true;

}

// Driver Code const a = [3, 5, 2, 5, 2]; const b = [2, 3, 5, 5, 2];

console.log(checkEqual(a, b) ? 'true' : 'false');

**Time Complexity: O(n), where n is the length of given array
**Auxiliary Space: O(n)

Check if two arrays are equal or not | DSA Problem