CODE 22: Minimum Depth of Binary Tree

Given a binary tree, find its minimum depth.

The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.

public int minDepth(TreeNode root) {// Start typing your Java solution below// DO NOT write main() functionif (null == root) {return 0;}Queue<TreeNode> queue = new LinkedList<TreeNode>();queue.offer(root);int layer = 1;int layerNumbers = 1;while (!queue.isEmpty()) {TreeNode node = queue.poll();layerNumbers--;if (null == node.left && null == node.right) {break;}if (null != node.left) {queue.offer(node.left);}if (null != node.right) {queue.offer(node.right);}if (layerNumbers == 0 && !queue.isEmpty()) {layerNumbers = queue.size();layer++;}}return layer;}