제출 #313597

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
313597		DoanPhuDuc	Palindrome-Free Numbers (BOI13_numbers)	C++14	100 / 100	1 ms	640 KiB

numbers

#include <iostream>
#include <vector>
#include <cstring>
#include <cassert>
#include <algorithm>

#define long long long

using namespace std;

const int D = 20;

long dp[D][11][11][2][2]; // (number_of_digits, pre_last_digit, last_digit, leading_not_zero, palindrome)

int a[40];

long DP(int n, int y, int x, int z, int pl) {
	if (n == 0) return !pl;
	long &ans = dp[n][y][x][z][pl];
	if (ans != -1) return ans;
	ans = 0;
	for (int d = 0; d < 10; ++d) {
		if (z == 1) {
			int p = y - z, q = x - z;
			// even-palin or odd-palin
			ans += DP(n - 1, x, d + 1, 1, pl | (q == d) | (p == d));

		} else ans += DP(n - 1, x, d + (z | (d > 0)), z | (d > 0), pl);
	}
	return ans;
} 

long Compute(long v) {
	int n = 0;
	while (v) {
		a[++n] = v % 10;
		v /= 10;
	}
	reverse(a + 1, a + n + 1);
	int pre_last_digit = -1, last_digit = -1, pl = 0;
	long ans = 0;
	for (int i = 1; i <= n; ++i) {
		for (int d = 0; d < a[i]; ++d) {
			if (i == 1 && d == 0) {
				// leading zero
				ans += DP(n - i, 0, 0, 0, 0);
			} else if (i == 1) {
				// d is a first digit
				long pre_ans = ans;;
				ans += DP(n - i, 0, d + 1, 1, 0);
				// cout << d << " = " << ans - pre_ans << '\n';
			} else {
				int p = pre_last_digit, q = last_digit;
				assert(last_digit != -1);
				// even-palin or odd-palin
				ans += DP(n - i, last_digit + 1, d + 1, 1, pl | (q == d) | (p == d));
			}
		}

		pl |= (a[i] == last_digit);
		pl |= (a[i] == pre_last_digit);

		pre_last_digit = last_digit;
		last_digit = a[i];
	}
	return ans;
}

void Brute(int l, int r) {
	int ans = 0;
	for (int i = l; i <= r; ++i) {
		// bool x = (i % 10) | ()
		if (i % 10 == i / 100) ++ans;
		else if (i / 100 == (i / 10) % 10) ++ans;
		else if ((i / 10) % 10 == i % 10) ++ans;
	}
	cout << "Brute: " << ans << '\n';
}

int main() {
	memset(dp, -1, sizeof dp);
	long l, r; cin >> l >> r;
	// Brute(100, 199);
	long y = Compute(r + 1);
	long x = Compute(l);
	// cout << y << " " << x << '\n';
	cout << y - x << '\n';
	return 0;
}

컴파일 시 표준 에러 (stderr) 메시지

numbers.cpp: In function 'long long int Compute(long long int)':
numbers.cpp:49:10: warning: unused variable 'pre_ans' [-Wunused-variable]
   49 |     long pre_ans = ans;;
      |          ^~~~~~~

• Subtask 1: 25 / 25
• Subtask 2: 75 / 75