HDU 4734 —— F(x)

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

int b[10], num[10];
int dp[10][4605];

int dfs(int u, int f, bool limit)
{
    if(u < 1)    return 1;
    if(!limit && dp[u][f] != -1)    return dp[u][f];
    
    int maxn = limit ? b[u] : 9;
    int ret = 0, cur;
    
    for(int i=0; i<=maxn; i++) {
        cur = f - i*(1<<u-1);
        if(cur > 0) {
            ret += dfs(u-1, cur, limit && i==maxn);
        } else if(cur == 0) {
            ret += 1;
        }
    }
    
    if(!limit)    dp[u][f] = ret;
    return ret;
}

int f(int n, int a)
{
    int lenb=0;
    memset(b, 0, sizeof(b));
    while(n) {
        b[++lenb] = n%10;
        n /= 10;
    }
    return dfs(lenb, a, 1);
}

int main ()
{
    num[0] = 1;
    for(int i=1; i<10; i++) {
        num[i] = num[i-1] * 10;
    }
    
    int T, A, B;
    scanf("%d", &T);
    memset(dp, -1, sizeof(dp));
    for(int kase=1; kase<=T; kase++) {
        scanf("%d%d", &A, &B);
        int base = 1, F=0;
        while(A) {
            F += base * (A % 10);
            
            base <<= 1;
            A /= 10;
        }
        printf("Case #%d: %d\n", kase, f(B, F));
    }
    return 0;
}