UVA 10718 Bit Mask

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <algorithm>
 5 #define sc3(x,y,z)  scanf("%lld%lld%lld", &x, &y, &z)
 6 #define pf(x)    printf("%lld\n",x)
 7 #define FOR(i,b,e)    for(int i=b;i<=e;i++)
 8 #define FOR1(i,b,e)    for(int i=b;i>=e;i--)
 9 #define CL(x,y)      memset(x,y,sizeof(x))
10 using namespace std;
11 typedef long long ll;
12 ll bit[35];
13 int a[35];
14 void init()
15 {
16     bit[0] = 1;
17     FOR(i,1,31)
18     {
19         bit[i] = 2 * bit[i-1];
20     }
21 }
22 int main()
23 {
24     ll N, L, U, MAX;
25     init();
26 //    cout << bit[0] << endl;
27     while(~sc3(N, L, U))
28     {
29         MAX = 0;
30         FOR(i,0,31)
31         {
32             a[i] = N % 2;
33             N /= 2;
34         }
35         FOR1(i,31,0)
36         {
37             MAX += bit[i];
38             if((a[i] == 0 && MAX > U) || (MAX > L && a[i] == 1))//后面的条件是考虑可适合范围中最小的max值 
39                 MAX -= bit[i];
40         }
41         pf(MAX);
42     }
43     return 0;
44 }