111. 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.

思路：min(leftHeight,rightHeight)+1递归

public class Solution {
    public int minDepth(TreeNode root) {
        if (root==null) return 0;
        if (root.left==null){
            return minDepth(root.right)+1;
        }
        if (root.right==null){
            return minDepth(root.left)+1;
        }
        return Math.min(minDepth(root.left),minDepth(root.right)) + 1;
    }
}