[51NOD1230]幸运数（数位DP）

题目链接：http://www.51nod.com/onlineJudge/questionCode.html#!problemId=1230

dp(l,s,ss)表示长度为l的数各位和为s，各位平方和为ss的幸运数的个数。

#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:10240000,10240000")
using namespace std;

typedef long long LL;
const int maxn = 22;
const int maxa = 162;
const int maxm = 1610;
LL l, r;
LL dp[maxn][maxa][maxm];
int digit[maxn];
bool isprime[maxm];

void printlist() {
  memset(isprime, true, sizeof(isprime));
  isprime[0] = isprime[1] = false;
  int pedge = int(sqrt(maxm));
  for(int i = 2; i <= pedge; i++) {
    if(isprime[i]) {
      int o = maxm / i;
      for(int j = 2; j <= o; j++) {
        isprime[i*j] = false;
      }
    }
  }
}

LL dfs(int l, int s, int ss, bool flag) {
  if(l == 0) return isprime[s] && isprime[ss];
  if(!flag && ~dp[l][s][ss]) return dp[l][s][ss];
  int pos = flag ? digit[l] : 9;
  LL ret = 0;
  for(int i = 0; i <= pos; i++) {
    ret += dfs(l-1, s+i, ss+i*i, flag&&(pos==i));
  }
  if(!flag) dp[l][s][ss] = ret;
  return ret;
}

LL f(LL x) {
  if(x < 0) return 0;
  int pos = 0;
  while(x) {
    digit[++pos] = x % 10;
    x /= 10;
  }
  return dfs(pos, 0, 0, true);
}

int main() {
  //freopen("in", "r", stdin);
  printlist();
  memset(dp, -1, sizeof(dp));
  int T;
  scanf("%d", &T);
  while(T--) {
    scanf("%lld%lld",&l,&r);
    printf("%lld
", f(r)-f(l-1));
  }
  return 0;
}