703.Kth Largest Element in a Stream

703.Kth Largest Element in a Stream

难度:Easy

Design a class to find the kth largest element in a stream. Note that it is the kth largest element in the sorted order, not the kth distinct element.

Your KthLargest class will have a constructor which accepts an integer k and an integer array nums, which contains initial elements from the stream. For each call to the method KthLargest.add, return the element representing the kth largest element in the stream.

Example:

int k = 3;
int[] arr = [4,5,8,2];
KthLargest kthLargest = new KthLargest(3, arr);
kthLargest.add(3);   // returns 4
kthLargest.add(5);   // returns 5
kthLargest.add(10);  // returns 5
kthLargest.add(9);   // returns 8
kthLargest.add(4);   // returns 8
Note: 
You may assume that nums' length ≥ k-1 and k ≥ 1.

使用最小堆完成，不过需要注意length< k的情况。这里补INT_MIN。

class KthLargest {
priority_queue<int,vector<int>,greater<int>>kth;
public:
    KthLargest(int k, vector<int>& nums) {
       
      
        for(auto n:nums)
            kth.push(n);
        for(int i=nums.size();i<k;i++)
            kth.push(INT_MIN);
        for(int i=0;i<int(nums.size())-k;i++)
          kth.pop();

    }
    
    int add(int val) {
        if(val>kth.top())
           {
               kth.pop();
               kth.push(val);
           }
     
        return kth.top();
    }
};

/**
 * Your KthLargest object will be instantiated and called as such:
 * KthLargest* obj = new KthLargest(k, nums);
 * int param_1 = obj->add(val);
 */

执行用时 :64 ms, 在所有 C++ 提交中击败了89.78%的用户 内存消耗 :19.3 MB, 在所有 C++ 提交中击败了87.57%的用户