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2350. Shortest Impossible Sequence of Rolls

Description

You are given an integer array rolls of length n and an integer k. You roll a k sided dice numbered from 1 to k, n times, where the result of the ith roll is rolls[i].

Return the length of the shortest sequence of rolls so that there's no such subsequence in rolls.

A sequence of rolls of length len is the result of rolling a k sided dice len times.

 

Example 1:

Input: rolls = [4,2,1,2,3,3,2,4,1], k = 4
Output: 3
Explanation: Every sequence of rolls of length 1, [1], [2], [3], [4], can be taken from rolls.
Every sequence of rolls of length 2, [1, 1], [1, 2], ..., [4, 4], can be taken from rolls.
The sequence [1, 4, 2] cannot be taken from rolls, so we return 3.
Note that there are other sequences that cannot be taken from rolls.

Example 2:

Input: rolls = [1,1,2,2], k = 2
Output: 2
Explanation: Every sequence of rolls of length 1, [1], [2], can be taken from rolls.
The sequence [2, 1] cannot be taken from rolls, so we return 2.
Note that there are other sequences that cannot be taken from rolls but [2, 1] is the shortest.

Example 3:

Input: rolls = [1,1,3,2,2,2,3,3], k = 4
Output: 1
Explanation: The sequence [4] cannot be taken from rolls, so we return 1.
Note that there are other sequences that cannot be taken from rolls but [4] is the shortest.

 

Constraints:

  • n == rolls.length
  • 1 <= n <= 105
  • 1 <= rolls[i] <= k <= 105

Solutions

Solution 1

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class Solution:
    def shortestSequence(self, rolls: List[int], k: int) -> int:
        ans = 1
        s = set()
        for v in rolls:
            s.add(v)
            if len(s) == k:
                ans += 1
                s.clear()
        return ans

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class Solution {
    public int shortestSequence(int[] rolls, int k) {
        Set<Integer> s = new HashSet<>();
        int ans = 1;
        for (int v : rolls) {
            s.add(v);
            if (s.size() == k) {
                s.clear();
                ++ans;
            }
        }
        return ans;
    }
}

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class Solution {
public:
    int shortestSequence(vector<int>& rolls, int k) {
        unordered_set<int> s;
        int ans = 1;
        for (int v : rolls) {
            s.insert(v);
            if (s.size() == k) {
                s.clear();
                ++ans;
            }
        }
        return ans;
    }
};

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func shortestSequence(rolls []int, k int) int {
    s := map[int]bool{}
    ans := 1
    for _, v := range rolls {
        s[v] = true
        if len(s) == k {
            ans++
            s = map[int]bool{}
        }
    }
    return ans
}

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