Codeforces 264A Buggy Sorting（童年排序）

最新推荐文章于 2020-07-28 15:01:37 发布

Shyazhut

最新推荐文章于 2020-07-28 15:01:37 发布

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分类专栏： CodeForces 一块水过这的题

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本文介绍了一个编程挑战，即找出一个排序算法的错误并提供反例。该算法由一位初学者编写，采用冒泡排序的方式对整数数组进行升序排列。文章提供了如何构造一个能够揭示算法缺陷的数据集的方法。

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Little boy Valera studies an algorithm of sorting an integer array. After studying the theory, he went on to the practical tasks. As a result, he wrote a program that sorts an array of n integers a1, a2, ..., an in the non-decreasing order. The pseudocode of the program, written by Valera, is given below. The input of the program gets number n and array a.

loop integer variable i from 1 to n - 1
    loop integer variable j from i to n - 1
        if (aj > aj + 1), then swap the values of elements aj and aj + 1

But Valera could have made a mistake, because he hasn't yet fully learned the sorting algorithm. If Valera made a mistake in his program, you need to give a counter-example that makes his program work improperly (that is, the example that makes the program sort the array not in the non-decreasing order). If such example for the given value of n doesn't exist, print -1.

Input

You've got a single integer n (1 ≤ n ≤ 50) — the size of the sorted array.

Output

Print n space-separated integers a1, a2, ..., an (1 ≤ ai ≤ 100) — the counter-example, for which Valera's algorithm won't work correctly. If the counter-example that meets the described conditions is impossible to give, print -1.

If there are several counter-examples, consisting of n numbers, you are allowed to print any of them.

         Examples
       
           input
         
1

           output
         
-1

题意：

给小明的程序找 bug 就是 heak吗？

思路：

其实真的没怎么看懂题目，自己英语和理解能力渣渣了。直接看代码->

AC CODE:

#include<stdio.h>
#include<cstring>
#include<algorithm>
#define HardBoy main()
#define ForMyLove return 0;
using namespace std;
const int MYDD = 1103;

int HardBoy {
	int n;
	scanf("%d", &n);
	
	if(n <= 2) puts("-1");
	else{
		while(n) {
			printf("%d ", n--);
		}
	}
	
	printf("\n");
	ForMyLove
}