Minimum Depth of Binary Tree

iteye_6755

于 2015-08-29 13:26:41 发布

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本文介绍了一种使用广度优先搜索算法求解二叉树最小深度的方法。通过迭代遍历的方式，从根节点开始一层层向下访问，直至找到最近的叶子节点，返回其路径长度即为最小深度。

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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.

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
	public int minDepth(TreeNode root) {
		if (root == null) {
			return 0;
		}
		int dep = 1;
		LinkedList<TreeNode> linkedList = new LinkedList<TreeNode>();
		linkedList.add(root);
		int cur = 1;
		int next = 0;
		while (!linkedList.isEmpty()) {
			TreeNode poll = linkedList.poll();
			cur--;
			if (poll.left == null && poll.right == null) {
				return dep;
			}
			if (poll.left != null) {
				linkedList.add(poll.left);
				next++;
			}
			if (poll.right != null) {
				linkedList.add(poll.right);
				next++;
			}
			if (cur == 0) {
				cur = next;
				next = 0;
				dep++;
			}
		}
		return dep;
	}
}