HDU 3555 Bomb(数位dp入门)

#include <bits/stdc++.h>
#define ll long long
using namespace std;
int a[20];
ll dp[20][10];

ll dfs(int pos, int pre, bool limit){
	if(pos == -1) return 1;
	if(!limit && dp[pos][pre] != -1) return dp[pos][pre];
	int up = limit ? a[pos] : 9;
	ll ans = 0;
	for(int i=0;i<=up;i++){
		if(pre == 4 && i == 9) continue;
		ans += dfs(pos - 1, i, limit && i == a[pos]);
	}
	return limit ? ans : dp[pos][pre] = ans;
}

ll solve(ll x){
	int pos = 0;
	while(x){
		a[pos++] = x % 10;
		x /= 10;
	}
	return dfs(pos - 1, 0, true);
}

int main()
{
	int T;
	memset(dp, -1, sizeof(dp));
	scanf("%d",&T);
	while(T--){
		ll n;
		scanf("%lld",&n);
		printf("%lld\n",n - solve(n) + 1);
	}
	return 0;
}