Submission #219583

#	Time	Username	Problem	Language	Result	Execution time	Memory
219583		socho	Palindrome-Free Numbers (BOI13_numbers)	C++14	100 / 100	12 ms	1024 KiB

numbers

#include "bits/stdc++.h"
using namespace std;
// #define endl '\n'
// #define double long double
#define int long long
// int MOD = 1000 * 1000 * 1000 + 7;
// int MOD = 998244353;
// const int MXN = 100005;

const int MXN = 20;
int digits[MXN];

void load(int a) {
	for (int i=19; i>=0; i--) {
		digits[i] = a % 10;
		a /= 10;
	}
}

int dp[MXN][2][MXN][10][10];

void dpclear() {
	for (int i=0; i<MXN; i++) {
		for (int j=0; j<2; j++) {
			for (int k=0; k<MXN; k++) {
				for (int a=0; a<10; a++) {
					for (int b=0; b<10; b++) {
						dp[i][j][k][a][b] = -1;
					}
				}
			}
		}
	}
}

int solve(int at, bool atmin, int placed, int last1, int last2) {
	if (at == MXN) return 1; // finished
	// cout << at << ' ' << atmin << ' ' << placed << ' ' << last1 << ' ' << last2 << endl;
	if (dp[at][atmin][placed][last1][last2] != -1) return dp[at][atmin][placed][last1][last2];
	int ans = 0;
	for (int i=0; i<=9; i++) {
		if (atmin && i > digits[at]) {
			// violates range
			continue;
		}
		else {
			bool mncond = atmin && (i == digits[at]);
			if (placed == 0) {
				// first digit, no restriction
				// cout << "tried placing: " << i << endl;
				if (i == 0) ans += solve(at+1, mncond, 0, i, 0);
				else ans += solve(at+1, mncond, placed+1, i, 0);
			}
			else if (placed == 1) {
				// second digit, only first restrict
				if (i != last1) {
					// cout << "tried placing: " << i << endl;
					ans += solve(at+1, mncond, placed+1, i, last1);
				}
			}
			else {
				// any other digit, all restrictions
				if (i != last1) {
					if (i != last2) {
						// cout << "tried placing: " << i << endl;
						ans += solve(at+1, mncond, placed+1, i, last1);
					}
				}
			}
			
		}
		
	}
	return dp[at][atmin][placed][last1][last2] = ans;
}

bool can(int a) {
    if (a <= 10) return true;
	string s = "";
	while (a > 0) {
		int x = a % 10;
		a /= 10;
		s += ((char) '0' + x);
	}
	for (int i=0; i<s.size()-1; i++) {
		if (s[i] == s[i+1]) return false;
	}
	for (int i=0; i<s.size()-2; i++) {
		if (s[i] == s[i+2]) return false;
	}
	return true;
	
}

signed main() {
	
	int a, b;
	cin >> a >> b;
	
	load(b);
	dpclear();
	
	int upto = solve(0, 1, 0, 0, 0);
	
	load(a);
	dpclear();
	int unto = solve(0, 1, 0, 0, 0);
	
	cout << upto - unto + can(a) << endl;
	
}

Compilation message (stderr)

numbers.cpp: In function 'bool can(long long int)':
numbers.cpp:85:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i=0; i<s.size()-1; i++) {
                ~^~~~~~~~~~~
numbers.cpp:88:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i=0; i<s.size()-2; i++) {
                ~^~~~~~~~~~~

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