标签：
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.
比较左子树和右子树的深度，取小的那个返回上来，并+1。
需要注意的是如果没有左子树或右子树。那么无条件取存在的那一边子树深度，并+1.
如果左子树和右子树都没有，那么就是叶子节点，返回深度1.
如果root自身为null,返回0
1 public int minDepth(TreeNode root) { 2 if(root==null) 3 return 0; 4 if(root.left==null && root.right==null) 5 return 1; 6 if(root.right==null) 7 return minDepth(root.left)+1; 8 if(root.left==null) 9 return minDepth(root.right)+1; 10 return Math.min(minDepth(root.right),minDepth(root.left))+1; 11 }
Balanced Binary Tree
Given a binary tree, determine if it is height-balanced.
For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.
新定义一个函数，表示树的高度，如果是平衡树的话。不是平衡树则置高度为-1. 运用分治法递归，最后得到结果为-1则不是平衡的。基本情况，root==null则高度为0
1 public boolean isBalanced(TreeNode root) { 2 if(height(root)==-1) 3 return false; 4 return true; 5 } 6 public int height(TreeNode root) 7 { 8 if(root==null) 9 return 0; 10 int left = height(root.left); 11 int right = height(root.right); 12 if(left==-1 || right==-1) 13 return -1; 14 if(Math.abs(left-right)>1) 15 return -1; 16 return Math.max(left,right)+1; 17 }
[Leetcode][JAVA] Minimum Depth of Binary Tree && Balanced Binary Tree
标签：
原文地址：http://www.cnblogs.com/splash/p/4401297.html
