[leetcode-295]Find Median from Data Stream(java)

问题描述：这里写链接内容

分析：这道题比较简单，重点在于如何高效插入数据。这里采用的是二分法，相当于插入排序。

代码如下：

class MedianFinder {
    List numlist  = new ArrayList<>();
    // Adds a number into the data structure.
    public void addNum(int num) {
        int left = 0;
        int right = numlist.size()-1;

        while(left<=right){
            int mid = (left+right)/2;
            int val = numlist.get(mid);

            if(val == num){
                numlist.add(mid,num);
                return;
            }else if(val < num){
                if(mid+1 < numlist.size() &&  numlist.get(mid+1)> num){
                    numlist.add(mid+1,num);
                    return;
                }
                left = mid+1;
            }else{
                right = mid-1;
            }
        }
        numlist.add(left,num);
    }

    // Returns the median of current data stream
    public double findMedian() {
        int size = numlist.size();
        if(size%2 == 1){//odd
            return numlist.get((size-1)/2);
        }
        return (numlist.get(size/2-1)+numlist.get(size/2))/2.0;
    }
};

// Your MedianFinder object will be instantiated and called as such:
// MedianFinder mf = new MedianFinder();
// mf.addNum(1);
// mf.findMedian();