LeetCode-in-Java

3680. Generate Schedule

Medium

You are given an integer n representing n teams. You are asked to generate a schedule such that:

• Each team plays every other team exactly twice: once at home and once away.
• There is exactly one match per day; the schedule is a list of consecutive days and schedule[i] is the match on day i.
• No team plays on consecutive days.

Return a 2D integer array schedule, where schedule[i][0] represents the home team and schedule[i][1] represents the away team. If multiple schedules meet the conditions, return any one of them.

If no schedule exists that meets the conditions, return an empty array.

Example 1:

Input: n = 3

Output: []

Explanation:

Since each team plays every other team exactly twice, a total of 6 matches need to be played: [0,1],[0,2],[1,2],[1,0],[2,0],[2,1].

It’s not possible to create a schedule without at least one team playing consecutive days.

Example 2:

Input: n = 5

Output: [[0,1],[2,3],[0,4],[1,2],[3,4],[0,2],[1,3],[2,4],[0,3],[1,4],[2,0],[3,1],[4,0],[2,1],[4,3],[1,0],[3,2],[4,1],[3,0],[4,2]]

Explanation:

Since each team plays every other team exactly twice, a total of 20 matches need to be played.

The output shows one of the schedules that meet the conditions. No team plays on consecutive days.

Constraints:

• 2 <= n <= 50

Solution

public class Solution {
    public int[][] generateSchedule(int n) {
        if (n < 5) {
            return new int[0][];
        }
        int[][] res = new int[n * (n - 1)][];
        int idx = 0;
        for (int i = 2; i < n - 1; i++) {
            for (int j = 0; j < n; j++) {
                res[idx++] = new int[] {j, (j + i) % n};
            }
        }
        for (int i = 0; i < n; i++) {
            res[idx++] = new int[] {i, (i + 1) % n};
            res[idx++] = new int[] {(i + 4) % n, (i + 3) % n};
        }
        return res;
    }
}

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