数据流的中位数

Posted 2022-01-31 Alice_yufeng

class MedianFinder 
    TreeMap<Integer, Integer> nums;
    int n;
    int[] left;
    int[] right;

    public MedianFinder() 
        nums = new TreeMap<Integer, Integer>();
        n = 0;
        left = new int[2];
        right = new int[2];
    
    
    public void addNum(int num) 
        nums.put(num, nums.getOrDefault(num, 0) + 1);
        if (n == 0) 
            left[0] = right[0] = num;
            left[1] = right[1] = 1;
         else if ((n & 1) != 0) 
            if (num < left[0]) 
                decrease(left);
             else 
                increase(right);
            
         else 
            if (num > left[0] && num < right[0]) 
                increase(left);
                decrease(right);
             else if (num >= right[0]) 
                increase(left);
             else 
                decrease(right);
                System.arraycopy(right, 0, left, 0, 2);
            
        
        n++;
    

    public double findMedian() 
        return (left[0] + right[0]) / 2.0;
    

    private void increase(int[] iterator) 
        iterator[1]++;
        if (iterator[1] > nums.get(iterator[0])) 
            iterator[0] = nums.ceilingKey(iterator[0] + 1);
            iterator[1] = 1;
        
    

    private void decrease(int[] iterator) 
        iterator[1]--;
        if (iterator[1] == 0) 
            iterator[0] = nums.floorKey(iterator[0] - 1);
            iterator[1] = nums.get(iterator[0]);
        
    


/**
 * Your MedianFinder object will be instantiated and called as such:
 * MedianFinder obj = new MedianFinder();
 * obj.addNum(num);
 * double param_2 = obj.findMedian();
 */