kth_largest_element_in_array.cpp

/*
215. Kth Largest Element in an Array
Medium

Find the kth largest element in an unsorted array. Note that it is the kth largest element in the sorted order, not the kth distinct element.

Example 1:

Input: [3,2,1,5,6,4] and k = 2
Output: 5

Example 2:

Input: [3,2,3,1,2,4,5,5,6] and k = 4
Output: 4

Note:
You may assume k is always valid, 1 ≤ k ≤ array's length.
*/

//Using sorting
class Solution {
public:
    static bool custom_sort(int a, int b){
        return a>b;    
    }
    
    int findKthLargest(vector<int>& nums, int k) {
        if(nums.size()==0 || k>nums.size())
            return -1;
        sort(nums.begin(), nums.end(), custom_sort);
        return nums[k-1];
    }
};

//Max-heap solution
class Solution{
    public :
    int findKthLargest(vector<int>& nums, int k){
        priority_queue<int> maxHeap;
        for(int el : nums){
            maxHeap.push(el);
        }
        for(int i=0;i<k-1;i++){
            maxHeap.pop();
        }
        return maxHeap.top();
    }
}