F(x)
Problem Description
For a decimal number x with n digits (AnAn-1An-2 ... A2A1), we define its weight as F(x) = An * 2n-1 + An-1 * 2n-2 + ... + A2 * 2 + A1 * 1. Now you are given two numbers A and B, please calculate how many numbers are there between 0 and B, inclusive, whose weight is no more than F(A).
Input
The first line has a number T (T <= 10000) , indicating the number of test cases.
For each test case, there are two numbers A and B (0 <= A,B < 109)
For each test case, there are two numbers A and B (0 <= A,B < 109)
Output
For every case,you should output "Case #t: " at first, without quotes. The t is the case number starting from 1. Then output the answer.
Sample Input
3
0 100
1 10
5 100
Sample Output
Case #1: 1
Case #2: 2
Case #3: 13
Source
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
#include <stdio.h> #include <vector> #include <string.h> using namespace std; vector <int> num; int dp[11][10000]; //dp状态设计成dp[pos][remain],remain表示还剩多少fA可以分配 int dfs(int pos, int remain, bool limit) //limit表示后面的数是否能乱填 { if (pos == -1) return remain >= 5000; if (!limit && ~dp[pos][remain]) return dp[pos][remain]; int end = limit?num[pos]:9; int res = 0; for (int i = 0; i <= end; i ++) { res += dfs(pos-1, remain-(1<<pos)*i, limit && (i == end)); } if (!limit) dp[pos][remain] = res; return res; } int main() { int t; scanf("%d", &t); memset(dp, -1,sizeof(dp)); for (int ca = 1; ca <= t; ca ++) { int A, B; scanf("%d %d", &A, &B); num.clear(); while(B) { num.push_back(B % 10); B /= 10; } int fa = 0; for (int i = 0; A; A /= 10, ++ i) fa += (1 << i) * (A % 10); printf("Case #%d: %d\n", ca, dfs(num.size()-1, 5000+fa, 1)); } return 0; }