Codeforces Round 104 (Div. 1)

Solutions for Codeforces Round 104 (Div. 1) (contest 145). 4/5 problems verified against sample I/O. Difficulty range: 1200-2900.

5 items

Codeforces Round 104 (Div. 1)

Type: Div. 1 | Problems: 5 | Verified: 4/5 | Rating range: 1200-2900 | Time: 10m 29s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Lucky Conversion	1200	greedy, implementation	2m 2s	✓
B	Lucky Number 2	1800	constructive-algorithms	2m 22s	✓
C	Lucky Subsequence	2100	combinatorics, dp, math	2m 5s	✓
D	Lucky Pair	2900	combinatorics, data-structures, implementation	1m 48s	✗
E	Lucky Queries	2400	data-structures	2m 12s	✓

Practice › Codeforces Solutions › Codeforces Round 104 (Div. 1) ›

CF 145A - Lucky Conversion

We are given two strings of equal length, both consisting only of the characters 4 and 7. The goal is to transform the first string into the second using the fewest operations. There are two allowed operations. We may flip a single digit, changing 4 to 7 or 7 to 4.

Practice › Codeforces Solutions › Codeforces Round 104 (Div. 1) ›

CF 145B - Lucky Number 2

We need to construct the lexicographically smallest lucky number consisting only of digits 4 and 7 such that four substring counts match given values.

Practice › Codeforces Solutions › Codeforces Round 104 (Div. 1) ›

CF 145C - Lucky Subsequence

We are given an array of integers and must count how many subsequences of length exactly k satisfy a special restriction on lucky numbers. A number is lucky if every decimal digit is either 4 or 7. Examples are 4, 47, and 744. Numbers like 5, 17, and 467 are not lucky.

Practice › Codeforces Solutions › Codeforces Round 104 (Div. 1) ›

CF 145D - Lucky Pair

We are given an array of integers, and some of these integers are "lucky numbers," meaning they consist only of the digits 4 and 7.

Practice › Codeforces Solutions › Codeforces Round 104 (Div. 1) ›

CF 145E - Lucky Queries

We have a string consisting only of digits 4 and 7. Two kinds of operations are performed on it. The first operation flips every digit in a segment. Every 4 becomes 7, and every 7 becomes 4.