A. Anti-knapsack

time limit per test1 second
memory limit per test256 megabytes
inputstandard input
outputstandard output
You are given two integers n and k. You are asked to choose maximum number of distinct integers from 1 to n so that there is no subset of chosen numbers with sum equal to k.

A subset of a set is a set that can be obtained from initial one by removing some (possibly all or none) elements of it.

Input
The first line contains the number of test cases T (1≤T≤100).

Each of the next T lines contains two integers n and k (1≤k≤n≤1000) — the description of test cases.

Output
For each test case output two lines. In the first line output a single integer m — the number of chosen integers.

In the second line output m distinct integers from 1 to n — the chosen numbers.

If there are multiple answers, print any. You can print the numbers in any order.

输入样例

3
3 2
5 3
1 1

输出样例

2
3 1 
3
4 5 2 
0

解题思路

选取最多数，使任意个数的所选数字之和不等于k
那么我们让最小的两个数相加都不等于k，且不存在单个数等于k
这里主要是对于k奇数和偶数的判定
不能简单地k/2
当k为奇数时，例如k=5,那么k/2=2，2+3=5
所以取奇数时我们要加一，我们可以用ceil函数直接搞定，这样连偶数的情况都不用考虑
（偶数的话k/2+（k+1）/2必定大于k;

AC代码

#include <iostream>
#include <cmath>
using namespace std;
int main() {
    
    
	int t;
	cin>>t;
	while(t--) {
    
    
		int n,k;
		cin>>n>>k;
		int cx =ceil((double)k/2);
		cout<<n-cx<<endl;
		for(int i=cx; i<=n; i++) {
    
    
			if(i==k)
			continue;
				cout<<i<<" ";
		}
		puts("");
	}
}