Submission #648464

#	Time	Username	Problem	Language	Result	Execution time	Memory
648464		glome	Palindrome-Free Numbers (BOI13_numbers)	C++17	39.17 / 100	1 ms	340 KiB

numbers

#include <bits/stdc++.h>

using namespace std;


string num;

int dp[19][11][11][2];

int mod = 1e9 + 7;

int rec(int pos, int p1, int p2, int f) {
    if(pos == num.size()) return 1;

    if(dp[pos][p1][p2][f] != -1) return dp[pos][p1][p2][f];

    int LIM = 9;
    if(!f) LIM = num[pos] - '0';

    int res = 0;
    for (int i = 0; i<=LIM; i++) {
        if(p1 == i || p2 == i) continue;
        res += rec(pos+1, i, p1, (f || i < LIM));
        if(res >= mod) res -= mod;
    }
    return dp[pos][p1][p2][f] = res;
}



int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    long long A, B;
    cin >> A >> B;
    num = to_string(B);
    if(A == 0) {
        memset(dp, -1 ,sizeof(dp));
        cout << rec(0, 10, 10, 0) << '\n';
    }
    else {
        A--;
        memset(dp, -1 ,sizeof(dp));

        B = rec(0, 10, 10, 0);

        memset(dp, -1, sizeof(dp)); num = to_string(A);

        cout << (B - rec(0, 10, 10, 0) + mod + mod) % mod << '\n';
    }
    return 0;
}

Compilation message (stderr)

numbers.cpp: In function 'int rec(int, int, int, int)':
numbers.cpp:13:12: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   13 |     if(pos == num.size()) return 1;
      |        ~~~~^~~~~~~~~~~~~

• Subtask 1: 12.5 / 25
• Subtask 2: 26.666666666666668 / 75