构造 CodeForces 483C Diverse Permutation

 1 /*
 2     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，
 3         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
 4 */
 5 /************************************************
 6 Author        :Running_Time
 7 Created Time  :2015-8-2 9:20:01
 8 File Name     :B.cpp
 9 *************************************************/
10 
11 #include <cstdio>
12 #include <algorithm>
13 #include <iostream>
14 #include <sstream>
15 #include <cstring>
16 #include <cmath>
17 #include <string>
18 #include <vector>
19 #include <queue>
20 #include <deque>
21 #include <stack>
22 #include <list>
23 #include <map>
24 #include <set>
25 #include <bitset>
26 #include <cstdlib>
27 #include <ctime>
28 using namespace std;
29 
30 typedef long long ll;
31 const int MAXN = 1e5 + 10;
32 const int INF = 0x3f3f3f3f;
33 const int MOD = 1e9 + 7;
34 bool vis[MAXN];
35 int a[MAXN];
36 
37 int main(void)    {       //CodeForces 483C Diverse Permutation
38     int n, k;
39     while (scanf ("%d%d", &n, &k) == 2) {
40         if (k == 1) {
41             for (int i=1; i<=n; ++i)    {
42                 printf ("%d%c", i, (i==n) ? ‘\n‘ : ‘ ‘);
43             }
44             continue;
45         }
46         memset (vis, false, sizeof (vis));
47         int j = 1;  a[0] = n;   vis[a[0]] = true;   bool flag = false;
48         for (int i=k; i>=1; --i)    {
49             if (flag)     {
50                 a[j] = a[j-1] + i;  vis[a[j]] = true;  ++j;     flag = !flag;
51             } 
52             else    {
53                 a[j] = a[j-1] - i;  vis[a[j]] = true;   j++;    flag = !flag;
54             }            
55         }
56         int p = n;
57         for (int i=j; i<n; ++i) {
58             for (int k=p; k>=1; --k)    {
59                 if (!vis[k])    {
60                     a[i] = k;   vis[k] = true; p = k; break;
61                 }
62             }
63         }
64         for (int i=0; i<n; ++i)    {
65             printf ("%d%c", a[i], (i==n-1) ? ‘\n‘ : ‘ ‘);
66         }
67     }
68 
69     return 0;
70 }