Leetcode: Possible Bipartition

Possible Bipartition



Similar Problems:


Given a set of N people (numbered 1, 2, …, N), we would like to split everyone into two groups of any size.

Each person may dislike some other people, and they should not go into the same group.

Formally, if dislikes[i] = [a, b], it means it is not allowed to put the people numbered a and b into the same group.

Return true if and only if it is possible to split everyone into two groups in this way.

Example 1:

Input: N = 4, dislikes = [[1,2],[1,3],[2,4]]
Output: true
Explanation: group1 [1,4], group2 [2,3]

Example 2:

Input: N = 3, dislikes = [[1,2],[1,3],[2,3]]
Output: false

Example 3:

Input: N = 5, dislikes = [[1,2],[2,3],[3,4],[4,5],[1,5]]
Output: false

Note:

  1. 1 <= N <= 2000
  2. 0 <= dislikes.length <= 10000
  3. 1 <= dislikes[i][j] <= N
  4. dislikes[i][0] < dislikes[i][1]
  5. There does not exist i != j for which dislikes[i] == dislikes[j].

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.


  • Solution:
// Blog link: https://code.dennyzhang.com/possible-bipartition
// Basic Ideas:
// Complexity: Time O(n), Space O(n)
func possibleBipartition(N int, dislikes [][]int) bool {
    m := map[int][]int{}
    for _, pair := range dislikes {
        n1, n2 := pair[0], pair[1]
        m[n1] = append(m[n1], n2)
        m[n2] = append(m[n2], n1)
    }

    types := make([]int, N+1)
    for i:=1; i<=N; i++ {
        if types[i] != 0 { continue }
        // put current node to one set
        types[i] = 1
        queue := []int{i}
        for len(queue) != 0 {
            l := []int{}
            for _, node := range queue {
                // get dislikes
                for _, node2 := range m[node] {
                    if types[node2] == types[node] { 
                        return false 
                    } else {
                        if types[node2] == 0 {
                            types[node2] = -types[node]
                            l = append(l, node2)
                        }
                    }
                }
            }
            queue = l
        }
    }
    return true
}
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