Submission #1771000

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

ll f(ll A){
	if(A == 0) return 0;
	string s = to_string(A);
	reverse(s.begin(), s.end());
	int N = s.size();
	vector<int> D(N);
	for(int i = 0; i < N; i++){
		D[i] = s[i] - '0';
	}

	// 桁、le、49
	ll num[20][2][2] = { 0 };
	num[0][1][0] = 1;
	for(int i = 0; i < N; i++){
		for(int j = 0; j < 2; j++){
			for(int k = 0; k < 2; k++){
				if(num[i][j][k] == 0) continue;
				for(int d = 0; d < 10; d++){
					int le = 0;
					if(j == 0 && d < D[i]) le = 1;
					if(j == 1 && d <= D[i]) le = 1;
					int nk = k || (d == 4 || d == 9);
					num[i + 1][le][nk] += num[i][j][k];
				}
			}
		}
	}
	return num[N][1][1];
}

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
#ifdef LOCAL
	std::ifstream in("in");
	std::cin.rdbuf(in.rdbuf());
#endif

	ll A, B;
	cin >> A >> B;
	cout << f(B) - f(A - 1) << endl;
}

Submission Info

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