HDU 4734 F(x)

#include<bits/stdc++.h>
using namespace std;

#define LL long long

const int maxn = 20;
int tw[maxn],num[maxn];
int dp[maxn][200000];

int dfs(int pos,bool bnd,int lef){
if(pos < 0) return lef >= 0;
if(lef < 0) return 0;
int &ndp = dp[pos][lef];
if(!bnd && ndp != -1){
return ndp;
}
int ret = 0;
int bound = bnd ? num[pos] : 9;
for(int i=0;i<=bound;i++){
if(i * tw[pos] > lef)
break;
ret += dfs(pos-1,bnd && i==bound,lef - i*tw[pos]);
}
if(!bnd)
ndp = ret;
return ret;
}

int cw(int x){
int ret = 0,len = 0;
while(x){
ret += tw[len]*(x%10);
x /= 10;
len++;
}
return ret;
}

int cal(int b,int a){
int len = 0;
a = cw(a);
while(b){
num[len++] = b % 10;
b /= 10;
}
return dfs(len-1,true,a);
}

int main(){
tw[0] = 1;
for(int i=1;i<maxn;i++){
tw[i] = tw[i-1]*2;
}
int icase = 1;
int T;
scanf("%d",&T);
int b,a;
memset(dp,-1,sizeof(dp));
while(T-- && ~scanf("%d %d",&a,&b)){
printf("Case #%d: %d\n",icase++,cal(b,a));
}
return 0;
}