所以说，我想练练线段树来着，结果这题二分就行了

所以说，我想练练线段树来着
但是一看这题，二分查找不就时间够了
结果写了个二分查找就过了
emmm继续找线段树题去
import java.util.*;

public class Solution {
    public ArrayList<Integer> smallerCount (ArrayList<Integer> nums) {
    	ArrayList<Integer> list = new ArrayList<Integer>();
    	ArrayList<Integer> ans = new ArrayList<Integer>();
    	for (int i =  nums.size()-1; i >= 0; i--) {
    		int num = nums.get(i);
    		ans.add(bs(list, num)+1);
			if(list.size()==0)
				list.add(num);
			else
				list.add(bs(list, num)+1, num);
		}
    	Collections.reverse(ans);
		return ans;
    }
    static int bs(ArrayList<Integer> list, int num) {
    	if(list.size()==0)
    		return -1;
    	int left = 0;
    	int right = list.size()-1;
    	while(left<right) {
    		int mid = (left + right+1)/2;
    		if(list.get(mid) < num)
    			left = mid;
    		else
    			right = mid -1;
    	}
    	if(list.get(0) >= num)
    		return -1;
    	return left;
    }
}