二叉树算法
1、如何定義一個二叉樹
通過遞歸的方式定義二叉樹:不能直接定義二叉樹,只能定義二叉樹結點。節點類的屬性包括當前節點的值、左子節點、右子節點(子節點的類型也是二叉樹結點類)、構造函數,代碼如下:
public class TreeNode {int val;TreeNode left;TreeNode right;TreeNode(int x) { val = x; } }2、深度優先搜索(前序搜索:根節點-左節點-右節點)
3、例題應用
1)求二叉樹的深度
采用DFS,先求左子樹的深度,再求右子樹的深度,返回
class Solution {public int maxDepth(TreeNode root) {if(root==null)return 0;int l_length = 1 , r_length = 1;l_length = maxDepth(root.left) + 1;r_length = maxDepth(root.right) + 1;return l_length>r_length?l_length:r_length;} }2)合并兩棵二叉樹
public class TreeNode {int val;TreeNode left;TreeNode right;TreeNode(int x) { val = x; } } class Solution {public TreeNode mergeTrees(TreeNode t1, TreeNode t2) {if(t1==null)return t2;if(t2==null)return t1;TreeNode new_merge_tree = new TreeNode(t1.val + t2.val);new_merge_tree.left = mergeTrees(t1.left,t2.left);new_merge_tree.right = mergeTrees(t1.right,t2.right);return new_merge_tree;} }?
總結
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