Codeforces Round 104 (Div. 2)

2 problems from Codeforces Round 104 (Div. 2) (contest 146), difficulty 800-1300. 2/2 solutions verified against sample I/O.

2 items

Codeforces Round 104 (Div. 2)

Div. 2 | 2 problems | 2/2 verified | Difficulty 800-1300 | 2m 40s

# Problem Rating Tags Accepted Time ✓
A Lucky Ticket 800 implementation 17,095 1m 10s ✓
B Lucky Mask 1300 brute-force, implementation 4,974 1m 30s ✓
Practice › Codeforces Solutions › Codeforces Round 104 (Div. 2) ›

CF 146A - Lucky Ticket

We are asked to determine whether a ticket number is lucky. A lucky ticket number satisfies two conditions simultaneously. First, every digit of the number must be either 4 or 7.
codeforces competitive-programming implementation May 29, 2026
Practice › Codeforces Solutions › Codeforces Round 104 (Div. 2) ›

CF 146B - Lucky Mask

We are given two integers. The first number, a, is arbitrary. The second number, b, is guaranteed to be lucky, meaning every digit of b is either 4 or 7. For any positive integer, its "mask" is formed by taking only the digits 4 and 7 from left to right and concatenating them.
codeforces competitive-programming brute-force implementation May 29, 2026