19(April) Find missing in second array

19. Find Missing in Second Array

The problem can be found at the following link: Question Link

Problem Description

Given two arrays a of size n and b of size m, the task is to find numbers which are present in the first array but not present in the second array.

Example:

Input:

n = 6, m = 5
a[] = {1, 2, 3, 4, 5, 10}
b[] = {2, 3, 1, 0, 5}

Output:

4 10

Explanation: 4 and 10 are present in the first array but not in the second array.

My Approach

1. Initialization:

• Create an unordered set s from the elements of array b.

1. Finding Missing Elements:

• Iterate through array a.

• For each element a[i], check if it exists in set s. If not, add it to the ans vector.

1. Return:

• Return the ans vector containing the missing elements.

Time and Auxiliary Space Complexity

• Expected Time Complexity: O(n + m), where n and m are the sizes of arrays a and b respectively. This complexity arises from iterating through both arrays once.

• Expected Auxiliary Space Complexity: O(m), where m is the size of array b, due to storing its elements in the unordered set.

Code (C++)

class Solution {
public:
    std::vector<int> findMissing(int a[], int b[], int n, int m) {
        std::unordered_set<int> s(b, b + m);
        std::vector<int> ans;

        for (int i = 0; i < n; ++i) {
            if (s.find(a[i]) == s.end()) {
                ans.push_back(a[i]);
            }
        }

        return ans;
    }
};

Contribution and Support

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