Dropping Balls UVA - 679

  A number of K balls are dropped one by one from the root of a fully binary tree structure FBT. Each time the ball being dropped first visits a non-terminal node. It then keeps moving down, either follows the path of the left subtree, or follows the path of the right subtree, until it stops at one of the leaf nodes of FBT. To determine a ball’s moving direction a flag is set up in every non-terminal node with two values, either false or true. Initially, all of the flags are false. When visiting a non-terminal node if the flag’s current value at this node is false, then the ball will first switch this flag’s value, i.e., from the false to the true, and then follow the left subtree of this node to keep moving down. Otherwise, it will also switch this flag’s value, i.e., from the true to the false, but will follow the right subtree of this node to keep moving down. Furthermore, all nodes of FBT are sequentially numbered, starting at 1 with nodes on depth 1, and then those on depth 2, and so on. Nodes on any depth are numbered from left to right.

  For example, Fig. 1 represents a fully binary tree of maximum depth 4 with the node numbers 1, 2, 3, ..., 15. Since all of the flags are initially set to be false, the first ball being dropped will switch flag’s values at node 1, node 2, and node 4 before it finally stops at position 8. The second ball being dropped will switch flag’s values at node 1, node 3, and node 6, and stop at position 12. Obviously, the third ball being dropped will switch flag’s values at node 1, node 2, and node 5 before it stops at

position 10.

  Fig. 1: An example of FBT with the maximum depth 4 and sequential node numbers.

  Now consider a number of test cases where two values will be given for each test. The first value is D, the maximum depth of FBT, and the second one is I, the I-th ball being dropped. You may assume the value of I will not exceed the total number of leaf nodes for the given FBT. Please write a program to determine the stop position P for each test case.

  For each test cases the range of two parameters D and I is as below:

2≤ D ≤20, and 1≤ I ≤524288.

Input

Contains l +2 lines.

Line 1 l the number of test cases

Line 2 D1 I1 test case #1, two decimal numbers that are separated by one blank

...

Line k +1 Dk Ik test case #k Line l +1 Dl Il test case #l

Line l +2 -1 a constant ‘-1’ representing the end of the input file

Output

Contains l lines.

Line 1 the stop position P for the test case #1

...

Line k the stop position P for the test case #k

...

Line l the stop position P for the test case #l

Sample Input

5
4 2
3 4
10 1
2 2
8 128
-1

Sample Output

12
7
512
3
255

HINT

这个题目最重要的是他的结论：

1. 给定一棵包含2 d 个结点（其中d 为树的高度）的完全二叉树，如果把结点从上到下从左到右编号为1,2,3……，则结点k 的左右子结点编号分别为2k 和2k +1。
2. 如果使用题目中给出的编号I ，则当I 是奇数时，它是往左走的第（I +1）/2个小球；当I 是偶数时，它是往右走的第I /2个小球。

Accepted

#include <bits/stdc++.h>
using namespace std;
int main()
{
	int s, m, n;
	while (cin >> s&&s!=-1) {
		while (s--){
			cin >> m >> n;
			unsigned long long int k = 1;
			for (int i = 0;i < m - 1;i++)
				if (n % 2) { k = k * 2;n = (n + 1) / 2; }
				else { k = k * 2 + 1;n /= 2; }
			cout<<k<<endl;
		}
	}
}