【每日一題】【DFS】【BFS】【佇列】2021年12月5日-199. 二叉樹的右檢視
阿新 • • 發佈:2021-12-05
解答:
/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode() {} * TreeNode(int val) { this.val = val; } * TreeNode(int val, TreeNode left, TreeNode right) { * this.val = val; * this.left = left; * this.right = right; * } * }*/ //BFS:層序遍歷保留每一層的最後一個節點 class Solution { public List<Integer> rightSideView(TreeNode root) { List<Integer> res = new ArrayList<>(); if(root == null) { return res; } Queue<TreeNode> queue = new LinkedList<>(); //入隊用offerqueue.offer(root); while(!queue.isEmpty()) { int size = queue.size(); for(int i = 0; i < size; i++) { TreeNode node = queue.poll(); if(node.left != null) { queue.offer(node.left); }if(node.right != null) { queue.offer(node.right); } if(i == size - 1) { res.add(node.val); } } } return res; } } //DFS:深度搜索,每一次的第一個加入 class Solution { public List<Integer> res = new ArrayList<>(); public List<Integer> rightSideView(TreeNode root) { dfs(root, 0); return res; } public void dfs(TreeNode root, int depth) { if(root == null) { return; } if(depth == res.size()) { res.add(root.val); } depth++; dfs(root.right, depth); dfs(root.left, depth); } }
本文來自部落格園,作者:劉金輝,轉載請註明原文連結:https://www.cnblogs.com/liujinhui/p/15646842.html