代码随想录算法刷题训练营day21

代码随想录算法刷题训练营day21：LeetCode(501)二叉搜索树中的众数、LeetCode(530)二叉搜索树的最小绝对差

LeetCode(501)二叉搜索树中的众数
题目
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代码

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;/*** 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;*     }* }*/
class Solution {public int[] findMode(TreeNode root) {//定义一个集合存储数据List<Integer> dateTree=new ArrayList<>();getDateTree(root,dateTree);Map<Integer,Integer> mapTreedate=new HashMap<>();for(int i=0;i<dateTree.size();i++){int tempDate=dateTree.get(i);if(mapTreedate.containsKey(tempDate)){mapTreedate.put(tempDate,mapTreedate.get(tempDate)+1);}else{mapTreedate.put(tempDate,1);}}//用Map集合存储数据int count=0;for(Map.Entry<Integer,Integer> entry:mapTreedate.entrySet()){int key=entry.getKey();int countValue=entry.getValue();if(countValue>=count){count=countValue;}}List<Integer> resultDate=new ArrayList<>();for(Map.Entry<Integer,Integer> entry:mapTreedate.entrySet()){if(entry.getValue().equals(count)){resultDate.add(entry.getKey());}}int[] result=new int[resultDate.size()];for(int i=0;i<resultDate.size();i++){result[i]=resultDate.get(i);}return result;}//遍历树public void getDateTree(TreeNode root,List<Integer> dateTree){if(root==null){return;}dateTree.add(root.val);getDateTree(root.left, dateTree);getDateTree(root.right, dateTree);}}

LeetCode(530)二叉搜索树的最小绝对差
题目
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代码

import java.util.ArrayList;
import java.util.List;/*** 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;*     }* }*/
class Solution {public int getMinimumDifference(TreeNode root) {List<Integer> dateTree=new ArrayList<>();getTreeDate(root,dateTree);int minDate=Math.abs(dateTree.get(0)-dateTree.get(1));for (int i = 0; i < dateTree.size(); i++) {for(int j=i+1;j<dateTree.size();j++){int tempDate=Math.abs(dateTree.get(i)-dateTree.get(j));if(tempDate<minDate){minDate=tempDate;}}        }return minDate;}public void getTreeDate(TreeNode root,List<Integer> dateTree){if(root==null){return;}dateTree.add(root.val);//中序getTreeDate(root.left, dateTree);getTreeDate(root.right, dateTree);}
}