02. First element to occur k times

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

My Approach

• We use an unordered map to store the frequency of each element while iterating through the array.

• At each step, we check if the frequency of the current element equals k. If it does, we return that element.

• If no such element is found, we return -1.

Time and Auxiliary Space Complexity

• Time Complexity: O(n) - We iterate through the array once.

• Auxiliary Space Complexity: O(n) - We use an unordered map to store the frequency of elements.

Code (C++)

class Solution {
public:
    int firstElementKTime(int n, int k, int a[]) {
        unordered_map<int,int> mp;
        for(int i = 0 ; i < n ; ++i){
            ++mp[a[i]];
            if(mp[a[i]] == k)
                return a[i];
        }
        return -1;
    }
};

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