【Leetcode】Minimum Depth of Binary Tree

题目链接：https://leetcode.com/problems/minimum-depth-of-binary-tree/

题目：

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.

思路：

注意递归传值的方式差异。

算法1：

int min = Integer.MAX_VALUE; //此处有bug 不过ac还是没问题的
    public int minDepth(TreeNode root) {
        
		if (root == null) {
			return 0;
		}
		findPath3(root, 0);
		return min;
	}

	public void findPath3(TreeNode p, int length) {
		if (p.left == null && p.right == null) {
			length++;
			if (length < min)
				min = length;
		}
		if (p.left != null)
			findPath3(p.left, length + 1);
		if (p.right != null)
			findPath3(p.right, length + 1);
	}

算法2：

public int minDepth(TreeNode root) {
		 if(root==null)
			 return 0;
		 if(root.left==null){//当左子树为空时，不能选择左(此时为0)右子树深度来比较最小深度，而要以右子树深度
			 return minDepth(root.right)+1;
		 }
		 if(root.right==null){
			 return minDepth(root.left)+1;
		 }
		 return Math.min(minDepth(root.left),minDepth(root.right))+1;
	 }