# 11.07.2023 [111. Minimum Depth of Binary Tree]

Count nodes in the shortest path from root to leaf

11.07.2023

111. Minimum Depth of Binary Tree easy
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Problem TLDR

Count nodes in the shortest path from root to leaf

Intuition

• remember to count nodes, not edges

• leaf is a node without children

• use BFS or DFS

Approach

Let’s use BFS

Complexity

• Time complexity:
  O(n)

• Space complexity:
  O(n)

Code

fun minDepth(root: TreeNode?): Int = with(ArrayDeque<TreeNode>()) {
    root?.let { add(it) }
    generateSequence(1) { (it + 1).takeIf { isNotEmpty() } }
    .firstOrNull {
        (1..size).any {
            with(poll()) {
                left?.let { add(it) }
                right?.let { add(it) }
                left == null && right == null
            }
        }
    } ?: 0
}