You are given an integer array nums and you have to return a new counts array. The counts array has the property where counts[i] is the number of smaller elements to the right of nums[i]. Example: Input: [5,2,6,1] Output: [2,1,1,0] Explanation: To the right of 5 there are 2 smaller elements (2 and 1). To the right of 2 there is only 1 smaller element (1). To the right of 6 there is 1 smaller element (1). To the right of 1 there is 0 smaller element. binary index https://www.youtube.com/watch?v=CWDQJGaN1gY https://www.youtube.com/watch?v=2SVLYsq5W8M&t=1084s Segment tree
315. Count of Smaller Numbers After Self
原文：https://www.cnblogs.com/tobeabetterpig/p/9913058.html