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.

这个题目的重点是如何处理最小值。应该将函数分为两部分一个是root == null 时返回0，判断不是叶子节点是返回一个极大值。

python

"""Definition of TreeNode:class TreeNode:    def __init__(self, val):        self.val = val        self.left, self.right = None, None"""class Solution:    """    @param root: The root of binary tree.    @return: An integer    """     def minDepth(self, root):        # write your code here        if root is None:            return 0        return self.getDepth(root)            def getDepth(self, root):        if root is None:            return sys.maxint        if root.left is None and root.right is None:            return 1        left = self.getDepth(root.left)        right = self.getDepth(root.right)        return 1 + min(left, right)

java

/** * Definition of TreeNode: * public class TreeNode { *     public int val; *     public TreeNode left, right; *     public TreeNode(int val) { *         this.val = val; *         this.left = this.right = null; *     } * } */public class Solution {    /**     * @param root: The root of binary tree.     * @return: An integer.     */    public int minDepth(TreeNode root) {        // write your code here        if (root == null) {            return 0;        }        return getDepth(root);    }    private int getDepth(TreeNode root) {        if (root == null) {            return Integer.MAX_VALUE;        }        if (root.left == null && root.right == null) {            return 1;        }        int left = getDepth(root.left);        int right = getDepth(root.right);        int depth = 1 + Math.min(left, right);        return depth;    }}