HDU - 4734 F(x) （2013成都网络游戏，数字DP）

#include <iostream>
#include <cstring>
#include <algorithm>
#include <cstdio>
using namespace std;

int A, B;
int dp[20][200000];
int bit[20];

int dfs(int cur, int num, int flag) {
if (cur == -1)
return num >= 0;
if (num < 0)
return 0;
if (!flag && dp[cur][num] != -1)
return dp[cur][num];
int ans = 0;
int end = flag?

bit[cur]:9;
for (int i = 0; i <= end; i++)
ans += dfs(cur-1, num-i*(1<<cur), flag&&i==end);
if (!flag)
dp[cur][num] = ans;
return ans;
}

int F(int x) {
int tmp = 0;
int len = 0;
while (x) {
tmp += (x%10)*(1<<len);
len++;
x /= 10;
}
return tmp;
}

int cal() {
int len = 0;
while (B) {
bit[len++] = B%10;
B /= 10;
}
return dfs(len-1, F(A), 1);
}

int main() {
int t;
int cas = 1;
scanf("%d", &t);
memset(dp, -1, sizeof(dp));
while (t--) {
scanf("%d%d", &A, &B);
printf("Case #%d: %d\n", cas++, cal());
}
return 0;
}