题目1: 求一棵二叉树的最大深度
Given a binary tree, find its maximum depth. The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.
/** * Definition for binary tree * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ //求二叉树的最大深度 public class Solution { public int maxDepth(TreeNode root) { if(root==null) return 0; int lDepth= maxDepth(root.left); int rDepth= maxDepth(root.right); return 1+( lDepth>rDepth ? lDepth: rDepth); //左右子树 选最大深度者(即使一侧没有节点也没关系 肯定选最大的 和0无关) } }
题目2:求一棵二叉树的最小深度(需要考虑一侧无子节点情况)
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 binary tree * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ public class Solution { public int run(TreeNode root) { if(root==null) return 0; int lDepth=run(root.left); int rDepth=run(root.right); if(lDepth==0 || rDepth==0) //需要考虑可能没有一侧子节点的情况 这样最小的是0 但只有根节点 不能算是到叶子节点的最短路径 return lDepth+rDepth+1; return 1+(lDepth< rDepth? lDepth: rDepth); } }