Submission #856998

#	Time	Username	Problem	Language	Result	Execution time	Memory
856998		MrMody	Palindrome-Free Numbers (BOI13_numbers)	C++17	100 / 100	1 ms	600 KiB

numbers

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define el "\n"
#define fio ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);

long long a,b;
bool used[22][2][10][10][2][2];
long long state[22][2][10][10][2][2];
int d[22],cnt;
 
int get_digits(long long n) {
    cnt=0;
    while(n) d[cnt++]=n%10,n/=10;
    reverse(d,d+cnt);
    return 0;
}
 
long long recurse(int pos, int f, int before_last, int last, int has_before_last, int has_last) {
    if(pos==cnt) return has_last;
    if(used[pos][f][before_last][last][has_before_last][has_last]) 
        return state[pos][f][before_last][last][has_before_last][has_last];
    long long ans=0;
    int i;
    for(i=0;i<10;i++) {
        if(f || i<=d[pos]){
            if(!has_last || last!=i){
                if(!has_before_last || before_last!=i) {
                    ans+=recurse(pos+1,f|(i<d[pos]),last,i,has_last,has_last|(i>0));
                }
            }
        }
    }
    used[pos][f][before_last][last][has_before_last][has_last] = true;
    state[pos][f][before_last][last][has_before_last][has_last] = ans;
    return ans;
}
 
long long f(long long n) {
    get_digits(n);
    memset(used,0,sizeof(used));
    return 1 + recurse(0,0,0,0,0,0);
}

int main() {
    fio
    cin >> a >> b;
    cout << f(b) - (a > 0 ? f(a-1):0);
    return 0;
}

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