Poj 2081 Recaman's Sequence之解题报告

 1 #include<cstdio>
 2 #include<iostream>
 3 #include<algorithm>
 4 #include<cstring>
 5 
 6 using namespace std;
 7 
 8 const int maxn = 500000+10;
 9 int a[maxn];
10 bool used[3012500];
11 
12 int  main(void)
13 {
14      int k,i,j;
15      
16      a[0] = 0;
17      memset(used,0,sizeof(used));
18      used[0] = 1;
19      for(i=1;i<=500000;++i)
20      {
21         if(a[i-1]-i>0&&!used[a[i-1]-i])  a[i] = a[i-1]-i;
22         else    a[i] = a[i-1]+i;
23         used[a[i]] = 1;
24      }
25      while(scanf("%d",&k),k!=-1)
26      {
27          
28          cout<<a[k]<<endl;
29      }
30      
31      return 0;
32 }