HUST 1600 Lucky Numbers

Description

Isun loves digit 4 and 8 very much. He thinks a number is lucky only if the number satisfy the following conditions: 
1.       The number only consists of digit 4 and 8. 
2.       The number multiples 48. 
One day, the math teacher gives Isun a problem: 
         Given L and R(1 <= L <= R <= 10^15), how many lucky numbers are there between L and R. (i.e. how many x satisfy L <= x <= R, x is a lucky number). 

Input

Multiple test cases. For each test case, there is only one line consist two numbers L and R. 

Output

For each test case, print the number of lucky numbers in one line. 
  
Do use the % lld specifier or cin/ cout stream to read or write 64-bit integers in С++. 

Sample Input

1 481 484848

Sample Output

1
7
直接预处理出全部的lucky number，然后每次询问可以直接二分找到区间，相减就是答案。
#include<cstdio>#include<string>#include<cstring>#include<vector>#include<iostream>#include<queue>#include<map>#include<bitset>#include<algorithm>using namespace std;typedef long long LL;const int INF = 0x7FFFFFFF;const int mod = 1e9 + 7;const int maxn = 3e5 + 10;LL l, r;LL a[maxn], tot;void dfs(int x, LL y){if (x == 15) return;if (y % 48 == 0) a[tot++] = y;dfs(x + 1, y * 10 + 4);dfs(x + 1, y * 10 + 8);}int main(){tot = 0; dfs(0, 0);sort(a, a + tot);while (scanf("%lld%lld", &l, &r) != EOF){int x = lower_bound(a, a + tot, l) - a;int y = upper_bound(a, a + tot, r) - a;printf("%d\n", y - x);}return 0;}