2225. Find Players With Zero or One Losses

Medium

You are given an integer array matches where matches[i] = [winneri, loseri] indicates that the player winneri defeated player loseri in a match.

Return a list answer of size 2 where:

• answer[0] is a list of all players that have not lost any matches.

• answer[1] is a list of all players that have lost exactly one match.

The values in the two lists should be returned in increasing order.

Note:

• You should only consider the players that have played at least one match.

• The testcases will be generated such that no two matches will have the same outcome.

Example 1:

Input: matches = [[1,3],[2,3],[3,6],[5,6],[5,7],[4,5],[4,8],[4,9],[10,4],[10,9]]
Output:
 [[1,2,10],[4,5,7,8]]
Explanation:
Players 1, 2, and 10 have not lost any matches.
Players 4, 5, 7, and 8 each have lost one match.
Players 3, 6, and 9 each have lost two matches.
Thus, answer[0] = [1,2,10] and answer[1] = [4,5,7,8].

Example 2:

Input: matches = [[2,3],[1,3],[5,4],[6,4]]
Output:
 [[1,2,5,6],[]]
Explanation:
Players 1, 2, 5, and 6 have not lost any matches.
Players 3 and 4 each have lost two matches.
Thus, answer[0] = [1,2,5,6] and answer[1] = [].

Constraints:

• 1 <= matches.length <= 105

• matches[i].length == 2

• 1 <= winneri, loseri <= 105

• winneri != loseri

• All matches[i] are unique.

解題

func findWinners(matches [][]int) [][]int {
    m := make(map[int]int)
    v := make(map[int]bool)

    for _, match := range matches {
        m[match[1]]++
        v[match[1]] = true
        v[match[0]] = true
    }

    res := [][]int{}
    res = append(res, []int{})
    res = append(res, []int{})

    for k := range v {
        if m[k] == 0 {
            res[0] = append(res[0], k)
        } else if m[k] == 1 {
            res[1] = append(res[1], k)
        }
    }

    sort.Ints(res[0])
    sort.Ints(res[1])

    return res
}