Submission #688341

#	Time	Username	Problem	Language	Result	Execution time	Memory
688341		stevancv	Palindrome-Free Numbers (BOI13_numbers)	C++14	98.33 / 100	1 ms	212 KiB

numbers

#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define sp ' '
#define en '\n'
#define smin(a, b) a = min(a, b)
#define smax(a, b) a = max(a, b)
using namespace std;
const int N = 800 + 2;
const int inf = 1e9;
ll dp[20][4];
/*
dp[i][0] - is the same string possible
dp[i][1] - only one position is used
dp[i][2] - >= 2 is used
*/
ll F(string a) {
    if (a == "0") return 0;
    dp[0][0] = 1;
    dp[0][1] = a[0] - '1';
    int x = a.size();
    for (int i = 1; i < x; i++) {
        dp[i][0] = dp[i - 1][0];
        if (a[i] == a[i - 1]) dp[i][0] = 0;
        if (i > 1 && a[i] == a[i - 2]) dp[i][0] = 0;
        dp[i][1] = 9;
        int k = a[i] - '0';
        if (a[i - 1] < a[i]) k -= 1;
        if (i > 1 && a[i - 2] < a[i]) k -= 1;
        dp[i][2] = k * dp[i - 1][0] + 9 * dp[i - 1][1] + 8 * dp[i - 1][2];
    }
    return dp[x - 1][0] + dp[x - 1][1] + dp[x - 1][2];
}
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    string a, b;
    cin >> a >> b;
    assert(a[0] != '0' || a.size() == 1);
    assert(b[0] != '0' || b.size() == 1);
    ll ans = F(b) - F(a);
    int ok = 1;
    for (int i = 0; i < a.size(); i++) {
        if (i > 1 && a[i] == a[i - 1]) ok = 0;
        if (i > 2 && a[i] == a[i - 2]) ok = 0;
    }
    cout << ans + ok << en;
    return 0;
}

Compilation message (stderr)

numbers.cpp: In function 'int main()':
numbers.cpp:44:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   44 |     for (int i = 0; i < a.size(); i++) {
      |                     ~~^~~~~~~~~~

• Subtask 1: 25 / 25
• Subtask 2: 73.33333333333333 / 75