gfg-podt 2/03/2024

"GFG PODT with my approch!!" -> Solution

First element to occur k times

Difficulty Level : Easy

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Given an array of n integers. Find the first element that occurs atleast k number of times.

Example 1:

Input :
n = 7, k = 2
a[] = {1, 7, 4, 3, 4, 8, 7}
Output :
4
Explanation :
Both 7 and 4 occur 2 times. But 4 is first that occurs twice.
As at index = 4, 4 has occurred twice whereas 7 appeared twice
at index 6.

Example 2:

Input :
n = 10, k = 3
a[] = {3, 1, 3, 4, 5, 1, 3, 3, 5, 4}
Output :
3
Explanation :
Here, 3 is the only number that appeared 3 times in the array.

Your Task:  
You don't need to read input or print anything. Your task is to complete the function firstElementKTime() which takes the array a[], its size n, and an integer k as input arguments and returns the required answer. If the answer is not present in the array, return -1.

Expected Time Complexity: O(n).
Expected Auxiliary Space: O(n).

Constraints:
1 <= n <= 10⁴
1 <= k <= 100
1<= a[i] <= 200

Topic Tags :
Arrays Hash Data Structures 

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)
       {
           break;
       }
   }
   
   for(auto x:mp)
   {
       if(x.second>=k)
       {
           return x.first;
       }
   }
   
   return -1;
  }
};