HDU 3555 Bomb(1-n含有“49”的数字个数)

#include <stdio.h>
#include <string.h>
#include <math.h>
#include <algorithm>
using namespace std;
typedef long long ll;

int T;
ll n;
int digit[20];
ll dp[20][10][2][2];

ll dfs(int pos, int pre, int state, int limit)
{
if (pos == -1) return state;
if (dp[pos][pre][state][limit] != -1) return dp[pos][pre][state][limit];
int last = limit ? digit[pos] : 9; // 是否已达数值上界
ll ret = 0;
for (int i = 0; i <= last; ++i) {
ret += dfs(pos - 1, i, state || (i == 9 && pre == 4), limit && i == last);
}
dp[pos][pre][state][limit] = ret;
return ret;
}

ll solve()
{
int len = 0;
memset(dp, -1, sizeof (dp));
memset(digit, 0, sizeof (digit));
while (n) {
digit[len++] = n % 10;
n /= 10;
}
return dfs(len - 1, 0, 0, 1);
}

int main()
{
scanf("%d", &T);
while (T--) {
scanf("%lld", &n);
printf("%lld\n", solve());
}
return 0;
}