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;
    }
}