hdu 5491(2015合肥网赛)The Next

题目;http://acm.hdu.edu.cn/showproblem.php?pid=5491

题意就是,T组测试数据。然后L，S1，S2。L的二进制中有x个1，x满足 S1<=x<=S2

求满足S1<=x<=S2

直接暴力,但是有个地方要注意,当L在递增枚举的过程中,X小于S1的时候,将其二进制中S1-X个0位转化成1,不然会超时

 1 #include<cstdio>
 2 using namespace std;
 3 typedef long long ll;
 4 int main()
 5 {
 6     ll t,ans=1,a[31],n,s1,s2;
 7     ll i,sum;
 8     scanf("%I64d",&t);
 9     while (t--)
10     {
11         scanf("%I64d %I64d %I64d",&n,&s1,&s2);
12         int flag=0;
13         while (1)
14         {
15             n++;
16             ll e=n;
17             i=0,sum=0;
18             while (e)
19             {
20                 a[++i]=e%2;
21                 if (e%2) sum++;
22                 e/=2;
23             }
24             if (sum<s1)
25             {
26                 ll q=s1-sum,j,w=0;
27                 for (j=1;j<=i;j++)
28                 {
29                     if (!a[j])
30                     {
31                         a[j]=1;
32                         w++;
33                     }
34                     if (w==q) break;
35                 }
36                 break;
37             }
38             if (sum<=s2&&sum>=s1)
39             {
40                 flag=1;
41                 break;
42             }
43         }
44         printf("Case #%I64d: ",ans++);
45         if (flag==1) printf("%I64d
",n);
46         else
47         {
48             sum=0;ll x=1;
49             for (ll j=1;j<=i;j++)
50             {
51                 sum+=x*a[j];
52                 x*=2;
53             }
54             printf("%I64d
",sum);
55         }
56     }
57     return 0;
58 }