295. Find Median from Data Stream

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Problem

The median is the middle value in an ordered integer list. If the size of the list is even, there is no middle value, and the median is the mean of the two middle values.

Implement the MedianFinder class:

  Example 1:

Input
["MedianFinder", "addNum", "addNum", "findMedian", "addNum", "findMedian"]
[[], [1], [2], [], [3], []]
Output
[null, null, null, 1.5, null, 2.0]

Explanation
MedianFinder medianFinder = new MedianFinder();
medianFinder.addNum(1);    // arr = [1]
medianFinder.addNum(2);    // arr = [1, 2]
medianFinder.findMedian(); // return 1.5 (i.e., (1 + 2) / 2)
medianFinder.addNum(3);    // arr[1, 2, 3]
medianFinder.findMedian(); // return 2.0

  Constraints:

  Follow up:

Solution

var MedianFinder = function() {
    this.arr = [];
};

/** 
 * @param {number} num
 * @return {void}
 */
MedianFinder.prototype.addNum = function(num) {
    if (!this.arr.length) {
        this.arr.push(num);
        return;
    }
    var left = 0;
    var right = this.arr.length - 1;
    while (left <= right) {
        if (left === right) {
            this.arr.splice(this.arr[left] >= num ? left : (left + 1), 0, num);
            return;
        }
        var mid = left + Math.floor((right - left) / 2);
        if (this.arr[mid] === num) {
            left = mid;
            right = mid;
        } else if (this.arr[mid] > num) {
            right = mid;
        } else {
            left = mid + 1;
        }
    }
};

/**
 * @return {number}
 */
MedianFinder.prototype.findMedian = function() {
    return this.arr.length % 2
        ? this.arr[(this.arr.length - 1) / 2]
        : (this.arr[this.arr.length / 2] + this.arr[this.arr.length / 2 - 1]) / 2;

};

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

Explain:

Binary search.

Complexity: