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whai 2024-01-30 23:56:04 +08:00
parent fac985ee27
commit d0f6cb7c3a
3 changed files with 257 additions and 0 deletions
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66
src/main/java/cn/whaifree/leetCode/Tree/LeetCode235.java Normal file
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package cn.whaifree.leetCode.Tree;
import cn.whaifree.leetCode.model.TreeNode;
import org.junit.Test;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/1/30 21:10
* @注释
*/
public class LeetCode235 {
@Test
public void test() {
TreeNode treeNode = TreeNode.constructTreeByArray(6,2,8,0,4,7,9,null,null,3,5);
new Solution().lowestCommonAncestor(treeNode, treeNode.left.right, treeNode.left).printTree();
}
class Solution {
/**
* 1. p,q在两边，直接返回
* 2. pq在左边，向左递归
* 3. pq在右边，向右递归
* @param root
* @param p
* @param q
* @return
*/
public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
// if (root == null) {
// return null;
// }
// if (root == p || root == q) {
// // 找到元素
// return root;
// }
// if (p.val < root.val && q.val > root.val) {
// return root;
// }
// if (p.val > root.val && q.val < root.val) {
// return root;
// }
// 只有这个有用
if (p.val > root.val && q.val > root.val) {
// 向右递归
return lowestCommonAncestor(root.right, p, q);
} else if (p.val < root.val && q.val < root.val) {
// 向左递归
return lowestCommonAncestor(root.left, p, q);
}
return root;
}
public TreeNode lowestCommonAncestor1(TreeNode root, TreeNode p, TreeNode q) {
if (root.val > p.val && root.val > q.val) return lowestCommonAncestor1(root.left, p, q);
if (root.val < p.val && root.val < q.val) return lowestCommonAncestor1(root.right, p, q);
return root;
}
}
}

100
src/main/java/cn/whaifree/leetCode/Tree/LeetCode236.java Normal file
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package cn.whaifree.leetCode.Tree;
import cn.whaifree.leetCode.model.TreeNode;
import org.junit.Test;
import java.util.ArrayList;
import java.util.List;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/1/30 17:35
* @注释
*/
public class LeetCode236 {
@Test
public void test() {
TreeNode treeNode = TreeNode.constructTreeByArray(1, 2, 3, 4, 5, 6);
new Solution1().lowestCommonAncestor(treeNode, treeNode.left.right, treeNode.left).printTree();
}
class Solution {
public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
// 先找到两个树
// 用两个List记录路径
// 挨个对比，找到最后一个公共的点
ArrayList<TreeNode> e1 = new ArrayList<>();
findNode(root, p, e1);
ArrayList<TreeNode> e2 = new ArrayList<>();
findNode(root, q, e2);
int minSize = Math.min(e1.size(), e2.size());
int index = minSize - 1;
while (index >= 0) {
if (e1.get(index) == e2.get(index)) {
return e1.get(index);
}
index--;
}
return null;
}
public boolean findNode(TreeNode root, TreeNode wantFindNode, List<TreeNode> path) {
if (root==null) return false;
path.add(root);
if (root == wantFindNode) {
return true;
}
boolean left = findNode(root.left, wantFindNode, path);
if (left == true) {
return true;
}
boolean right = findNode(root.right, wantFindNode, path);
if (right == true) {
return true;
}
path.remove(path.size() - 1);
return left || right;
}
}
class Solution1 {
public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
if (root==null) return null;
// 左右找到两个树
// 如果找到树了，返回该节点
if (root.val == p.val || root.val == q.val) {
return root;
}
TreeNode left = lowestCommonAncestor(root.left, p, q);
TreeNode right = lowestCommonAncestor(root.right, p, q);
if(left == null && right == null) { // 若未找到节点 p 或 q
return null;
}else if(left == null && right != null) { // 若找到一个节点
return right;
}else if(left != null && right == null) { // 若找到一个节点
return left;
}else { // 若找到两个节点
return root;
}
}
}
}

91
src/main/java/cn/whaifree/leetCode/Tree/LeetCode501.java Normal file
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package cn.whaifree.leetCode.Tree;
import cn.whaifree.leetCode.model.TreeNode;
import org.junit.Test;
import java.util.ArrayList;
import java.util.List;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/1/30 11:07
* @注释
*/
public class LeetCode501 {
class Solution {
List<Integer> res = new ArrayList<>();
int maxFrequency = 0;
public int[] findMode(TreeNode root) {
circle(root, 0);
return null;
}
public void circle(TreeNode root, int maxFrequency) {
if (root == null) {
return;
}
if (root.right != null && root.right.val == root.val) {
}
}
}
@Test
public void test() {
TreeNode root = TreeNode.constructTreeByArray(6,2,8,0,4,7,9,null,null,2,6);
for (int i : new Solution1().findMode(root)) {
System.out.println(i);
}
}
class Solution1 {
List<Integer> res = new ArrayList<>();
// 记录当前出现次数最多的
int max = 0;
TreeNode pre = null;
int sum = 0;
public int[] findMode(TreeNode root) {
circle(root);
int size = res.size();
int[] r = new int[size];
for (int i = 0; i < size; i++) {
r[i] = res.get(i);
}
return r;
}
public void circle(TreeNode root) {
if (root == null) {
return;
}
circle(root.left);
int rootValue = root.val;
// 如果当前节点是root，那么pre就是左节点
// 如果当前节点是right,那么pre就是root
if (pre == null || rootValue != pre.val) {
sum = 1;
}else {
sum++;
}
// 如果出现次数比当前已经有的最大值都多，那么重新统计
if (sum > max) {
max = sum;
res.clear();
res.add(rootValue);
} else if (sum == max) {
res.add(rootValue);
}
// 记录上一个节点
pre = root;
circle(root.right);
}
}
}