Codeforces Round #395 (Div. 2) B
Description
Young Timofey has a birthday today! He got kit of n cubes as a birthday present from his parents. Every cube has a number ai, which is written on it. Timofey put all the cubes in a row and went to unpack other presents.
In this time, Timofey's elder brother, Dima reordered the cubes using the following rule. Suppose the cubes are numbered from 1 to n in their order. Dima performs several steps, on step i he reverses the segment of cubes from i-th to (n - i + 1)-th. He does this whilei ≤ n - i + 1.
After performing the operations Dima went away, being very proud of himself. When Timofey returned to his cubes, he understood that their order was changed. Help Timofey as fast as you can and save the holiday — restore the initial order of the cubes using information of their current location.
The first line contains single integer n (1 ≤ n ≤ 2·105) — the number of cubes.
The second line contains n integers a1, a2, ..., an ( - 109 ≤ ai ≤ 109), where ai is the number written on the i-th cube after Dima has changed their order.
Print n integers, separated by spaces — the numbers written on the cubes in their initial order.
It can be shown that the answer is unique.
7
4 3 7 6 9 1 2
2 3 9 6 7 1 4
8
6 1 4 2 5 6 9 2
2 1 6 2 5 4 9 6
Consider the first sample.
- At the begining row was [2, 3, 9, 6, 7, 1, 4].
- After first operation row was [4, 1, 7, 6, 9, 3, 2].
- After second operation row was [4, 3, 9, 6, 7, 1, 2].
- After third operation row was [4, 3, 7, 6, 9, 1, 2].
- At fourth operation we reverse just middle element, so nothing has changed. The final row is [4, 3, 7, 6, 9, 1, 2]. So the answer for this case is row [2, 3, 9, 6, 7, 1, 4].
题意:给我们交换后的数组,告诉我们交换规则1~n中(1,n交换,2,n-1交换....),然后是2~n-1中(2,n-1交换......),直到中间位置,问我们初始数组是怎么排列的
解法:偶数位置是不动的,奇数位置需要调换就好了
#include<bits/stdc++.h>
using namespace std;
#define ll long long
int main()
{
int b[];
int n;
//vector<int>q;
cin>>n;
int a[];
for(int i=; i<=n; i++)
{
cin>>a[i];
}
if(n%)
{
for(int i=;i<=n/;i++)
{
if(i&)
{
swap(a[i],a[n-i+]);
}
}
for(int i=;i<=n;i++)
{
cout<<a[i]<<" ";
}
}
else if(n!=&&n%==)
{
for(int i=;i<=n/;i++)
{
if(i&)
{
swap(a[i],a[n-i+]);
}
}
for(int i=;i<=n;i++)
{
cout<<a[i]<<" ";
}
}
else
{
cout<<a[]<<" "<<a[]<<endl;
}
return ;
}
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