构造 Codeforces Round #275 (Div. 2) C. Diverse Permutation

题目传送门

 /*
     构造：首先先选好k个不同的值，从1到k，按要求把数字放好，其余的随便放。因为是绝对差值，从n开始一下一上，
         这样保证不会超出边界并且以防其余的数相邻绝对值差>k
 */
 /************************************************
 Author        :Running_Time
 Created Time  :2015-8-2 9:20:01
 File Name     :B.cpp
 *************************************************/

 #include <cstdio>
 #include <algorithm>
 #include <iostream>
 #include <sstream>
 #include <cstring>
 #include <cmath>
 #include <string>
 #include <vector>
 #include <queue>
 #include <deque>
 #include <stack>
 #include <list>
 #include <map>
 #include <set>
 #include <bitset>
 #include <cstdlib>
 #include <ctime>
 using namespace std;

 typedef long long ll;
 const int MAXN = 1e5 + ;
 const int INF = 0x3f3f3f3f;
 const int MOD = 1e9 + ;
 bool vis[MAXN];
 int a[MAXN];

 int main(void)    {       //Codeforces Round #275 (Div. 2) C. Diverse Permutation
     int n, k;
     while (scanf ("%d%d", &n, &k) == ) {
         if (k == ) {
             for (int i=; i<=n; ++i)    {
                 printf ("%d%c", i, (i==n) ? '\n' : ' ');
             }
             continue;
         }
         memset (vis, false, sizeof (vis));
         int j = ;  a[] = n;   vis[a[]] = true;   bool flag = false;
         for (int i=k; i>=; --i)    {
             if (flag)     {
                 a[j] = a[j-] + i;  vis[a[j]] = true;  ++j;     flag = !flag;
             }
             else    {
                 a[j] = a[j-] - i;  vis[a[j]] = true;   j++;    flag = !flag;
             }
         }
         int p = n;
         for (int i=j; i<n; ++i) {
             for (int k=p; k>=; --k)    {
                 if (!vis[k])    {
                     a[i] = k;   vis[k] = true; p = k; break;
                 }
             }
         }
         for (int i=; i<n; ++i)    {
             printf ("%d%c", a[i], (i==n-) ? '\n' : ' ');
         }
     }

     return ;
 }