Leetcode 703. Kth Largest Element in a Stream

文章作者：Tyan
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1. Description

Kth Largest Element in a Stream

2. Solution

• Version 1

class KthLargest {
public:
    KthLargest(int k, vector nums) {
        this->k = k;
        sort(nums.begin(), nums.end());
        this->nums = nums;
    }
    
    int add(int val) {
        int pos = binarySearch(val);
        nums.insert(nums.begin() + pos, val);
        return nums[nums.size() - k];
    }

private:
    int k;
    vector nums;
    
    int binarySearch(int val) {
        int left = 0;
        int right = nums.size() - 1;
        while(left <= right) {
            int mid = (left + right) / 2;
            if(nums[mid] == val) {
                return mid;
            }
            else if(nums[mid] > val) {
                right = mid - 1;
            }
            else {
                left = mid + 1;
            }
        }
        return left;
    }
    
};

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

• Version 2

class KthLargest {
public:
    KthLargest(int k, vector nums) {
        this->k = k;
        sort(nums.begin(), nums.end(), greater());
        if(nums.size() > k) {
            nums.resize(k);
        } 
        this->nums = nums;
    }
    
    int add(int val) {
        if(nums.size() == 0) {
            nums.push_back(val);
            return nums[k - 1];
        }
        if(val <= nums[k - 1] && nums.size() == k) {
            return nums[k - 1];
        }
        int pos = binarySearch(val);
        nums.insert(nums.begin() + pos, val);
        if(nums.size() > k) {
            nums.pop_back();
        }
        return nums[k - 1];
    }

private:
    int k;
    vector nums;
    
    int binarySearch(int val) {
        int left = 0;
        int right = nums.size() - 1;
        while(left <= right) {
            int mid = (left + right) / 2;
            if(nums[mid] == val) {
                return mid;
            }
            else if(nums[mid] < val) {
                right = mid - 1;
            }
            else {
                left = mid + 1;
            }
        }
        return left;
    }
    
};

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

• Version 3

class KthLargest {
public:
    KthLargest(int k, vector nums) {
        this->k = k;
        for(int i = 0; i < nums.size(); i++) {
            pq.push(nums[i]);
            if(pq.size() > k) {
                pq.pop();
            }
        }
    }
    
    int add(int val) {
        pq.push(val);
        if(pq.size() > k) {
            pq.pop();
        }
        return pq.top();
    }

private:
    int k;
    priority_queue, greater > pq;
    
};

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

Reference

1. https://leetcode.com/problems/kth-largest-element-in-a-stream/description/