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whai 2024-03-31 11:34:29 +08:00
parent 2cfc6687bf
commit c4248f2cfe
17 changed files with 1093 additions and 2 deletions
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232
src/main/java/cn/whaifree/interview/Meituan/MT3_39.java Normal file
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@ -0,0 +1,232 @@
package cn.whaifree.interview.Meituan;
import java.util.*;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/3/30 19:09
* @注释
*/
public class MT3_39 {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int k = scanner.nextInt();
int x = scanner.nextInt();
int y = scanner.nextInt();
// xz + x = tl
// yd - y = xz
// xz + yd + tl = k
int tl = (k - 2 * x - y) / 3;
int xz = tl + x;
int yd = xz + y;
System.out.print(tl + " " + yd + " " + xz);
}
static class p2{
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int n = scanner.nextInt();
int[] nums = new int[n];
int max = Integer.MIN_VALUE;
for (int i = 0; i < n; i++) {
nums[i] = scanner.nextInt();
max = Math.max(max, nums[i]);
}
for (int num : nums) {
if (num * 2 > max) {
System.out.print(num * 2);
System.out.print(" ");
} else {
System.out.print(max);
System.out.print(" ");
}
}
}
}
static class p4{
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
String s1 = scanner.next();
String s2 = scanner.next();
char[] c1 = s1.toCharArray();
char[] c2 = s2.toCharArray();
// 遇到不一样的就对前面全部不一样的操作
int index = s1.length()-1;
int flag = 0;
for (int i = 0; i < c1.length; i++) {
if (c1[i] == c1[i + 1] && c2[i] != c2[i + 1]) {
flag = 0;
break;
} else if (c1[i] != c1[i + 1] && c2[i] == c2[i + 1]) {
flag = 1;
break;
} else if (c1[i] != c1[i + 1] && c2[i] != c2[i + 1]) {
flag = 2;
break;
}
}
if (flag == 0) {
List<String> list = new ArrayList<>();
while (index >= 0) {
if (c1[index]!= c2[index]) {
for (int i = index; i >= 0; i--) {
c2[i] = c1[index];
}
list.add("2 " + (index + 1) + " " + c1[index]);
}
index--;
}
System.out.println(list.size());
list.forEach(System.out::println);
} else {
List<String> list2 = new ArrayList<>();
index = s1.length() - 1;
c1 = s1.toCharArray();
c2 = s2.toCharArray();
while (index >= 0) {
if (c2[index]!= c1[index]) {
for (int i = index; i >= 0; i--) {
c1[i] = c2[index];
}
list2.add("1 " + (index + 1) + " " + c2[index]);
}
index--;
}
System.out.println(list2.size());
list2.forEach(System.out::println);
}
}
}
static class p5{
static long res = 0;
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int n = scanner.nextInt();
String s = scanner.next();
char[] chars = s.toCharArray();
HashMap<Character, Integer> map = new HashMap<>();
backTacking(chars, 0, map);
System.out.println(res);
}
public static void backTacking(char[] chars, int start, Map<Character,Integer> map) {
if (map.size() == 2 && isEqualValue(map)) {
res++;
}
if (start > chars.length || map.size() > 2) {
return;
}
for (int i = start; i < chars.length; i++) {
map.put(chars[i], map.getOrDefault(chars[i], 0) + 1);
backTacking(chars, i + 1, map);
Integer integer = map.get(chars[i]);
if (integer == 1) {
map.remove(chars[i]);
}else {
map.put(chars[i], map.get(chars[i]) - 1);
}
}
}
public static boolean isEqualValue(Map<Character, Integer> map) {
// 判断map的所有value是否一样
for (Integer value : map.values()) {
if (value != map.values().iterator().next()) {
return false;
}
}
return true;
}
}
// static class p6{
// static int res = 0;
// public static void main(String[] args) {
//
// Scanner scanner = new Scanner(System.in);
// int n = scanner.nextInt();
// String s = scanner.next();
// char[] chars = s.toCharArray();
//
// ArrayList<Integer> map = new ArrayList<>();
// backTacking(chars, 0, map);
// System.out.println(res);
// }
//
// public static void backTacking(char[] chars, int start, ArrayList<Integer> map) {
// if (map.size() == 2 && isEqualValue(map)) {
// res++;
// }
// if (start > chars.length || map.size() > 2) {
// return;
// }
//
// for (int i = start; i < chars.length; i++) {
// map;
// backTacking(chars, i + 1, map);
// Integer integer = map.get(chars[i]);
// if (integer == 1) {
// map.remove(chars[i]);
// }else {
// map.put(chars[i], map.get(chars[i]) - 1);
// }
// }
// }
//
// public static boolean isEqualValue(Map<Character, Integer> map) {
// // 判断map的所有value是否一样
// for (Integer value : map.values()) {
// if (value != map.values().iterator().next()) {
// return false;
// }
// }
// return true;
// }
// }
static class p7{
/**
* 小美有n个朋友，她准备请其中一些朋友来吃饭。
* 其中有一些朋友有暗恋关系：假设a暗恋b，那么小美带上b的时候a也必须去，否则a就会不开心。
* 小美想知道，一共有多少种不同的请客方案可以让每个人都开心？由于答案可能过大，请对10^9+7取模。
* @param args
*/
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int peopleNumber = scanner.nextInt();
int relation = scanner.nextInt();
int[] rela = new int[peopleNumber + 1];
for (int i = 0; i < relation; i++) {
int from = scanner.nextInt();
int to = scanner.nextInt();
rela[from] = to;
}
// rela 表示 index的人暗恋 里面值的那个
// 1 2
// 2 3
// 3 4
}
}
}

92
src/main/java/cn/whaifree/interview/XieChen/xc328.java
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@ -1,5 +1,6 @@
package cn.whaifree.interview.XieChen; package cn.whaifree.interview.XieChen;
import java.util.ArrayList;
import java.util.Arrays; import java.util.Arrays;
import java.util.Scanner; import java.util.Scanner;
@ -77,8 +78,12 @@ public class xc328 {
} }
// 将偶数的区间/2 让整个区间最大 /**
public static void main(String[] args) { * 将偶数的区间/2 让整个区间最大
* 给定一个数组，对一个区间（区间内全部都是偶数）全部/2，使得整个数组和最小
* @param args
*/
public static void main1(String[] args) {
Scanner in = new Scanner(System.in); Scanner in = new Scanner(System.in);
int n = in.nextInt(); int n = in.nextInt();
long[] nums = new long[n]; long[] nums = new long[n];
@ -129,6 +134,89 @@ public class xc328 {
} }
System.out.println(sum - minSum / 2); System.out.println(sum - minSum / 2);
} }
/**
* 2 -2 4 -8 5
* @param args
*/
public static void main(String[] args) {
String s = new String("abc") + new String("cde");
Scanner in = new Scanner(System.in);
int n = in.nextInt();
long[] nums = new long[n];
for (int i = 0; i < n; i++) {
nums[i] = in.nextLong();
}
// 获取前缀和
long[] preSum = new long[n + 1];
for (int i = 1; i < n + 1; i++) {
preSum[i] = preSum[i - 1] + nums[i - 1];
}
// 找到最小区间
// 用求最大连续子串和的思想求出array中连续的最小的负值
// 2 -4 -2 8 1
// 遇到区间总和>0的直接跳过
long nowSum = 0;
long minSum = Integer.MAX_VALUE;
// 滑动窗口，让窗口内的值都为偶数，并且是总和最小的窗口
for (int i = 0; i < nums.length; i++) {
for (int j = i; j < nums.length; j++) {
if (Math.abs(nums[j] % 2) == 1) {
break;
}
nowSum += nums[j];
minSum = Math.min(nowSum, minSum);
if (nowSum > 0) {
// 最大连续子串和的思想：
// 我们要找到最小的负数区间（即负的越多越好），
// 如果加上某个区间后，这个区间的值为整数，必然这个区间是会让整体区间变大，所以直接不取这个区间
break;
}
}
nowSum = 0;
}
long sum = 0;
for (long num : nums) {
sum += num;
}
System.out.println(sum - minSum / 2);
}
public static void main43(String[] args) {
Scanner scanner = new Scanner(System.in);
int n = scanner.nextInt();
ArrayList<Integer> nums = new ArrayList<>();
long ans = 0;
for (int i = 0; i < n; ++i) {
int t = scanner.nextInt();
nums.add(t);
ans += t;
}
int left = 0, right = 0;
long tsum = 0;
long minum = 0;
while (right < n) {
if ((nums.get(right) & 1) == 1 || tsum + nums.get(right) >= 0) {
right++;
left = right;
tsum = 0;
} else {
tsum += nums.get(right);
minum = Math.min(minum, tsum);
right++;
}
// System.out.println(tsum);
}
System.out.println(ans - (minum / 2));
}
} }
static class p4{ static class p4{

1
src/main/java/cn/whaifree/leetCode/Hash/LeetCode202.java
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@ -90,6 +90,7 @@ public class LeetCode202 {
Set<Integer> set = new HashSet<>(); Set<Integer> set = new HashSet<>();
while (n != 1) { while (n != 1) {
n = getNextNumber(n); n = getNextNumber(n);
System.out.println(n);
if (set.contains(n)) { if (set.contains(n)) {
return false; return false;
} else { } else {

9
src/main/java/cn/whaifree/redo/redoAll/2024_3_30.md Normal file
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@ -0,0 +1,9 @@
[LeetCode206.java](LeetCode206.java)
[LeetCode18.java](LeetCode18.java)
[LeetCode209.java](LeetCode209.java)
[LeetCode202.java](LeetCode202.java)
[LeetCode15.java](LeetCode15.java)
水平遍历 [LeetCode94_145_144_102.java](LeetCode94_145_144_102.java)

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src/main/java/cn/whaifree/redo/redoAll/LeetCode15.java Normal file
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@ -0,0 +1,63 @@
package cn.whaifree.redo.redoAll;
import org.junit.Test;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/3/30 15:35
* @注释
*/
public class LeetCode15 {
@Test
public void test()
{
Solution solution = new Solution();
int[] nums = new int[]{-2,0,0,2,2};
List<List<Integer>> lists = solution.threeSum(nums);
System.out.println(lists);
}
class Solution {
public List<List<Integer>> threeSum(int[] nums) {
List<List<Integer>> res = new ArrayList<>();
Arrays.sort(nums);
for (int i = 0; i < nums.length; i++) {
if (i > 0 && nums[i] == nums[i - 1]) {
continue;
}
int left = i + 1;
int right = nums.length - 1;
while (left < right) {
int sum = nums[i] + nums[left] + nums[right];
if (sum == 0) {
res.add(Arrays.asList(nums[i], nums[left], nums[right]));
while (left < right && nums[left] == nums[left + 1]) {
left++;
}
while (left < right && nums[right] == nums[right - 1]) {
right--;
}
left++;
right--;
} else if (sum > 0) {
right--;
}else {
left++;
}
}
}
return res;
}
}
}

35
src/main/java/cn/whaifree/redo/redoAll/LeetCode151.java Normal file
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@ -0,0 +1,35 @@
package cn.whaifree.redo.redoAll;
import org.junit.Test;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/3/30 13:51
* @注释
*/
public class LeetCode151 {
@Test
public void test()
{
Solution solution = new Solution();
String s = " hello ";
String s1 = solution.reverseWords(s);
System.out.println(s1);
}
class Solution {
public String reverseWords(String s) {
// s = " hello world "
// 去除前后空白串
s = s.trim();
String[] split = s.split("\\s+"); // 活着 " +"
StringBuilder stringBuilder = new StringBuilder();
for (int i = split.length - 1; i > 0; i--) {
stringBuilder.append(split[i]).append(" ");
}
stringBuilder.append(split[0]);
return stringBuilder.toString();
}
}
}

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src/main/java/cn/whaifree/redo/redoAll/LeetCode18.java Normal file
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@ -0,0 +1,76 @@
package cn.whaifree.redo.redoAll;
import org.junit.Test;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/3/30 12:46
* @注释
*/
public class LeetCode18 {
@Test
public void test()
{
int[] nums = {-1,0,-5,-2,-2,-4,0,1,-2};
int target = -9;
Solution solution = new Solution();
List<List<Integer>> lists = solution.fourSum(nums, target);
System.out.println(lists);
}
class Solution {
public List<List<Integer>> fourSum(int[] nums, int target) {
Arrays.sort(nums);
List<List<Integer>> res = new ArrayList<>();
if (nums[0] > target && nums[0] > 0) {
return res;
}
for (int i = 0; i < nums.length; i++) {
// 重复去除
if (i > 0 && nums[i] == nums[i - 1]) {
continue;
}
for (int j = i + 1; j < nums.length; j++) {
// 第一次给过
if (j > i + 1 && nums[j] == nums[j - 1]) {
continue;
}
int left = j + 1;
int right = nums.length - 1;
while (left < right) {
int sum = nums[i] + nums[j] + nums[left] + nums[right];
if (sum == target) {
res.add(Arrays.asList(nums[i], nums[j], nums[left], nums[right]));
while (right > left && nums[left] == nums[left+ 1]) {
left++;
}
while (right > left && nums[right] == nums[right - 1]) {
right--;
}
left++;
right--;
} else if (sum > target) {
right--;
}else {
left++;
}
}
}
}
return res;
}
}
}

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src/main/java/cn/whaifree/redo/redoAll/LeetCode202.java Normal file
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@ -0,0 +1,44 @@
package cn.whaifree.redo.redoAll;
import org.junit.Test;
import java.util.HashSet;
import java.util.Set;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/3/30 15:29
* @注释
*/
public class LeetCode202 {
@Test
public void test() {
Solution solution = new Solution();
boolean happy = solution.isHappy(2);
System.out.println(happy);
}
class Solution {
public boolean isHappy(int n) {
Set<Integer> set = new HashSet<>();
while (n > 1) {
if (set.contains(n)) return false;
set.add(n);
n = get(n);
}
return true;
}
public int get(int n) {
int res = 0;
while (n > 0) {
int retail = n % 10;
res += retail * retail;
n /= 10;
}
return res;
}
}
}

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src/main/java/cn/whaifree/redo/redoAll/LeetCode209.java Normal file
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@ -0,0 +1,42 @@
package cn.whaifree.redo.redoAll;
import org.junit.Test;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/3/30 14:53
* @注释
*/
public class LeetCode209 {
@Test
public void test() {
int[] nums = {1,2,3,4,5};
int target = 11;
int minSubArrayLen = new Solution().minSubArrayLen(target, nums);
System.out.println(minSubArrayLen);
}
class Solution {
public int minSubArrayLen(int target, int[] nums) {
int nowSum = 0;
int left = 0;
int right = 0;
int minLength = Integer.MAX_VALUE;
while (right < nums.length) {
nowSum += nums[right];
while (nowSum >= target) {
minLength = Math.min(right - left + 1, minLength);
nowSum -= nums[left];
left++;
}
right++;
}
return minLength == Integer.MAX_VALUE ? 0 : minLength;
}
}
}

73
src/main/java/cn/whaifree/redo/redoAll/LeetCode225.java Normal file
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@ -0,0 +1,73 @@
package cn.whaifree.redo.redoAll;
import org.junit.Test;
import java.util.Deque;
import java.util.LinkedList;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/3/30 16:11
* @注释
*/
public class LeetCode225 {
@Test
public void test()
{
MyStack myStack = new MyStack();
myStack.push(1);
myStack.push(2);
myStack.push(3);
myStack.push(4);
myStack.push(5);
System.out.println(myStack.pop());
System.out.println(myStack.pop());
System.out.println(myStack.pop());
System.out.println(myStack.top());
}
class MyStack {
Deque<Integer> queue1;
Deque<Integer> queue2;
public MyStack() {
queue1 = new LinkedList<>();
queue2 = new LinkedList<>();
}
public void push(int x) {
queue1.add(x);
}
public int pop() {
while (queue1.size() != 1) {
queue2.add(queue1.pop());
}
Integer pop = queue1.pop();
while (!queue2.isEmpty()) {
queue1.add(queue2.pop());
}
return pop;
}
public int top() {
return queue1.peekLast();
}
public boolean empty() {
return queue1.isEmpty();
}
}
/**
* Your MyStack object will be instantiated and called as such:
* MyStack obj = new MyStack();
* obj.push(x);
* int param_2 = obj.pop();
* int param_3 = obj.top();
* boolean param_4 = obj.empty();
*/
}

68
src/main/java/cn/whaifree/redo/redoAll/LeetCode232.java Normal file
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@ -0,0 +1,68 @@
package cn.whaifree.redo.redoAll;
import org.junit.Test;
import java.util.ArrayDeque;
import java.util.Deque;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/3/30 16:23
* @注释
*/
public class LeetCode232 {
@Test
public void test() {
MyQueue myQueue = new MyQueue();
myQueue.push(1); // queue is: [1]
myQueue.push(2); // queue is: [1, 2] (leftmost is front of the queue)
System.out.println(myQueue.peek()); // return 1
System.out.println(myQueue.pop()); // return 1, queue is [2]
System.out.println(myQueue.empty()); // return false
}
class MyQueue {
Deque<Integer> stack1;
Deque<Integer> stack2;
public MyQueue() {
stack1 = new ArrayDeque<>();
stack2 = new ArrayDeque<>();
}
public void push(int x) {
stack1.push(x);
}
public int pop() {
while (!stack1.isEmpty()) {
stack2.push(stack1.pop());
}
Integer pop = stack2.pop();
while (!stack2.isEmpty()) {
stack1.push(stack2.pop());
}
return pop;
}
public int peek() {
return stack1.peekLast();
}
public boolean empty() {
return stack1.isEmpty();
}
}
/**
* Your MyQueue object will be instantiated and called as such:
* MyQueue obj = new MyQueue();
* obj.push(x);
* int param_2 = obj.pop();
* int param_3 = obj.peek();
* boolean param_4 = obj.empty();
*/
}

54
src/main/java/cn/whaifree/redo/redoAll/LeetCode2487.java Normal file
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@ -0,0 +1,54 @@
package cn.whaifree.redo.redoAll;
import cn.whaifree.leetCode.model.ListNode;
import org.junit.Test;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/3/30 12:31
* @注释
*/
public class LeetCode2487 {
@Test
public void test() {
new Solution().removeNodes(ListNode.listNodeFromArray(new int[]{5})).printList();
}
class Solution {
/**
* 移除每个右侧有一个更大数值的节点。
* 逆转后，移除左侧更小的节点
* @param head
* @return
*/
public ListNode removeNodes(ListNode head) {
ListNode reverse = reverse(head);
ListNode index = reverse;
while (index.next != null) {
if (index.next.val < index.val) {
index.next = index.next.next;
}else {
index = index.next;
}
}
return reverse(reverse);
}
public ListNode reverse(ListNode head) {
return rev(null, head);
}
public ListNode rev(ListNode before, ListNode after) {
if (after == null) {
return before;
}
ListNode next = after.next;
after.next = before;
return rev(after, next);
}
}
}

32
src/main/java/cn/whaifree/redo/redoAll/LeetCode28.java Normal file
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@ -0,0 +1,32 @@
package cn.whaifree.redo.redoAll;
import org.junit.Test;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/3/30 13:41
* @注释
*/
public class LeetCode28 {
@Test
public void test() {
Solution solution = new Solution();
int i = solution.strStr("ab", "a");
System.out.println(i);
}
class Solution {
public int strStr(String haystack, String needle) {
int length = needle.length();
for (int i = 0; i < haystack.length() - length + 1; i++) {
if (haystack.substring(i, i + length).equals(needle)) {
return i;
}
}
return -1;
}
}
}

71
src/main/java/cn/whaifree/redo/redoAll/LeetCode287.java Normal file
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@ -0,0 +1,71 @@
package cn.whaifree.redo.redoAll;
import org.junit.Test;
import java.util.HashSet;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/3/30 11:40
* @注释
*/
public class LeetCode287 {
@Test
public void test()
{
int[] nums = {3,1,3,4,2};
int i = new Solution1().findDuplicate(nums);
System.out.println(i);
}
class Solution {
public int findDuplicate(int[] nums) {
HashSet<Integer> map = new HashSet<>();
for (int num : nums) {
if (map.contains(num)) {
return num;
}else {
map.add(num);
}
}
return -1;
}
}
class Solution1 {
/**
* 循环链表的入口
* 0 1 2 3 4
* 3 1 3 4 2
*
* 0 3 4 2 3
*
* 0-->1--->3---->2--->4
* |----|
*
* @param nums
* @return
*/
public int findDuplicate(int[] nums) {
int fast = 0;
int slow = 0;
do {
fast = nums[nums[fast]];
slow = nums[slow];
}
while (fast != slow);
// 此时找到交会点
fast = 0;
while (fast != slow) {
fast = nums[fast];
slow = nums[slow];
}
return fast;
}
}
}

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src/main/java/cn/whaifree/redo/redoAll/LeetCode347.java Normal file
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package cn.whaifree.redo.redoAll;
import org.junit.Test;
import java.util.HashMap;
import java.util.PriorityQueue;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/3/30 16:54
* @注释
*/
public class LeetCode347 {
@Test
public void test()
{
Solution solution = new Solution();
int[] nums = {1,1,1,2,2,3};
int k = 2;
int[] res = solution.topKFrequent(nums, k);
for (int i = 0; i < res.length; i++) {
System.out.println(res[i]);
}
}
class Solution {
public int[] topKFrequent(int[] nums, int k) {
// 频率统计
HashMap<Integer, Integer> map = new HashMap<>();
for (int i = 0; i < nums.length; i++) {
map.put(nums[i], map.getOrDefault(nums[i], 0) + 1);
}
PriorityQueue<Integer> queue = new PriorityQueue<>(
k, (o1, o2) -> map.get(o2) - map.get(o1)
);
for (Integer integer : map.keySet()) {
queue.add(integer);
}
int[] res = new int[k];
for (int i = 0; i < res.length; i++) {
res[i] = queue.poll();
}
return res;
}
}
}

146
src/main/java/cn/whaifree/redo/redoAll/LeetCode94_145_144_102.java Normal file
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package cn.whaifree.redo.redoAll;
import cn.whaifree.leetCode.model.TreeNode;
import org.junit.Test;
import java.util.ArrayList;
import java.util.Deque;
import java.util.LinkedList;
import java.util.List;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/3/30 17:48
* @注释
*/
public class LeetCode94_145_144_102 {
@Test
public void test(
) {
new Solution().levelOrder(TreeNode.constructTreeByArray(1,2,3,4,5,6)).forEach(
System.out::println
);
}
class Solution {
public List<Integer> inorderTraversal(TreeNode root) {
List<Integer> list = new ArrayList<>();
circle(root, list);
return list;
}
public void circle(TreeNode treeNode, List<Integer> list) {
if (treeNode == null) {
return;
}
circle(treeNode.left, list);
list.add(treeNode.val);
circle(treeNode.right, list);
}
public List<Integer> inorderTraversal1(TreeNode root) {
List<Integer> list = new ArrayList<>();
if (root == null) {
return list;
}
Deque<TreeNode> stack = new LinkedList<>();
stack.push(root);
while (!stack.isEmpty()) {
TreeNode pop = stack.pop();
if (pop == null) {
TreeNode index = stack.pop();
list.add(index.val);
}else {
// 第一次进入，加入null标签
if (pop.right!=null) stack.push(pop.right);
stack.push(pop);
stack.push(null);
if (pop.left!=null) stack.push(pop.left);
}
}
return list;
}
// 后序遍历
public List<Integer> inorderTraversal2(TreeNode root) {
List<Integer> list = new ArrayList<>();
if (root == null) {
return list;
}
Deque<TreeNode> stack = new LinkedList<>();
stack.push(root);
while (!stack.isEmpty()) {
TreeNode pop = stack.pop();
if (pop == null) {
TreeNode index = stack.pop();
list.add(index.val);
}else {
// 第一次进入，加入null标签
stack.push(pop);
stack.push(null);
if (pop.right!=null) stack.push(pop.right);
if (pop.left!=null) stack.push(pop.left);
}
}
return list;
}
public List<Integer> inorderTraversal3(TreeNode root) {
List<Integer> list = new ArrayList<>();
if (root == null) {
return list;
}
Deque<TreeNode> stack = new LinkedList<>();
stack.push(root);
while (!stack.isEmpty()) {
TreeNode pop = stack.pop();
list.add(pop.val);
if (pop.right != null) {
stack.push(pop.right);
}
if (pop.left != null) {
stack.push(pop.left);
}
}
return list;
}
public List<List<Integer>> levelOrder(TreeNode root) {
List<List<Integer>> res = new ArrayList<>();
if (root == null) {
return res;
}
Deque<TreeNode> deque = new LinkedList();
deque.add(root);
while (!deque.isEmpty()) {
int size = deque.size();
List<Integer> e = new ArrayList<>();
for (int i = 0; i < size; i++) {
TreeNode pop = deque.pop();
e.add(pop.val);
if (pop.left!=null) deque.add(pop.left);
if (pop.right!=null) deque.add(pop.right);
}
res.add(e);
}
return res;
}
}
}

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目录.md Normal file
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# 目录
- [main](#main)
- [test](#test)