CODE 22. Minimum Depth of Binary Tree

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版权声明：本文为博主原创文章，转载请注明出处：http://blog.jerkybible.com/2013/09/19/2013-09-19-CODE 22 Minimum Depth of Binary Tree/

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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() function
	if (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;
}