LightOJ 1140 How Many Zeroes? (数位DP)

#pragma comment(linker, "/STACK:1024000000,1024000000")
#include <cstdio>
#include <string>
#include <cstdlib>
#include <cmath>
#include <iostream>
#include <cstring>
#include <set>
#include <queue>
#include <algorithm>
#include <vector>
#include <map>
#include <cctype>
#include <cmath>
#include <stack>
#define freopenr freopen("in.txt", "r", stdin)
#define freopenw freopen("out.txt", "w", stdout)
using namespace std;

typedef long long LL;
typedef pair<int, int> P;
const int INF = 0x3f3f3f3f;
const double inf = 0x3f3f3f3f3f3f;
const double PI = acos(-1.0);
const double eps = 1e-8;
const int maxn = 1e5 + 5;
const int mod = 1e9 + 7;
const int dr[] = {-1, 0, 1, 0};
const int dc[] = {0, 1, 0, -1};
const char *de[] = {"0000", "0001", "0010", "0011", "0100", "0101", "0110", "0111", "1000", "1001", "1010", "1011", "1100", "1101", "1110", "1111"};
int n, m;
const int mon[] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
const int monn[] = {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
inline int Min(int a, int b){ return a < b ? a : b; }
inline int Max(int a, int b){ return a > b ? a : b; }
inline LL Min(LL a, LL b){ return a < b ? a : b; }
inline LL Max(LL a, LL b){ return a > b ? a : b; }
inline bool is_in(int r, int c){
return r >= 0 && r < n && c >= 0 && c < m;
}
LL dp[15][15];
int a[15];

LL dfs(int pos, int num, bool is, bool ok){
if(!pos)  return is ? 1 : num;
LL &ans = dp[pos][num];
if(!ok && ans >= 0 && !is)  return ans;

LL res = 0;
int n = ok ? a[pos] : 9;
for(int i = 0; i <= n; ++i){
if(is)  res += dfs(pos-1, num, !i, ok && i == n);
else if(!i)  res += dfs(pos-1, num+1, false, ok && i == n);
else res += dfs(pos-1, num, false, ok && i == n);
}
if(!ok && !is)  ans = res;
return res;
}

LL solve(LL n){
if(n == -1)  return 0;
int len = 0;
while(n > 0){
a[++len] = n % 10;
n /= 10;
}
return dfs(len, 0, true, true);
}

int main(){
memset(dp, -1, sizeof dp);
LL x, y;
int T;  cin >> T;
for(int kase = 1; kase <= T; ++kase){
scanf("%lld %lld", &x, &y);
printf("Case %d: %lld\n", kase, solve(y)-solve(x-1));
}
return 0;
}