Binary Tree Level Order Traversal - LeetCode 102

binary_tree_level_order.go

func levelOrder(root *TreeNode) [][]int {
    if root == nil {
        return nil
    }
    
    q := []*TreeNode{root}
    var result [][]int
    
    for len(q) != 0 {
        size := len(q)
        var currLvl []int
        
        for i := 0; i < size; i++ {
            curr := q[len(q)-1]
            if len(q) != 0 { 
                q = q[:len(q)-1] 
            }
            currLvl = append(currLvl, curr.Val)
            
            if curr.Left != nil {
                q = append([]*TreeNode{curr.Left}, q...)
            }
            if curr.Right != nil {
                q = append([]*TreeNode{curr.Right}, q...)
            }
        }
        result = append(result, currLvl)
    }
    
    return result
}