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Copy pathNumber103BFS.java
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156 lines (131 loc) · 4.4 KB
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package weekSix;
import java.util.*;
public class Number103BFS {
public static void main(String[] args) {
}
public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
return null;
}
// 查看套路模版
public List<List<Integer>> levelOrder(TreeNode root) {
List<List<Integer>> allResults = new ArrayList<>();
if (root == null) {
return allResults;
}
Queue<TreeNode> nodes = new LinkedList<>();
nodes.add(root);
int sign = 0;
while (!nodes.isEmpty()) {
int size = nodes.size();
List<Integer> results = new ArrayList<>();
// sign 0 从左到右 1从右到左
for (int i = 0; i < size; i++) {
TreeNode node = nodes.poll();
results.add(node.val);
if (sign == 0) {
if (node.right != null) {
nodes.add(node.right);
}
if (node.left != null) {
nodes.add(node.left);
}
sign = 1;
continue;
}
if (node.left != null) {
nodes.add(node.left);
}
if (node.right != null) {
nodes.add(node.right);
}
sign = 0;
}
allResults.add(results);
}
return allResults;
}
public class TreeNode {
int val;
TreeNode left;
TreeNode right;
TreeNode(int x) {
val = x;
}
}
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
List<List<Integer>> allResults = new ArrayList<>();
if (root == null) {
return allResults;
}
Queue<TreeNode> nodes = new LinkedList<>();
nodes.add(root);
int sign = 0;
while (!nodes.isEmpty()) {
int size = nodes.size();
Deque<Integer> results = new LinkedList<>();
// sign 0 从左到右 1从右到左
for (int i = 0; i < size; i++) {
TreeNode node = nodes.poll();
results.add(node.val);
if (node.left != null) {
nodes.add(node.left);
}
if (node.right != null) {
nodes.add(node.right);
}
if (sign == 0) {
results.offerLast(node.val);
continue;
}
results.offerFirst(node.val);
}
sign = sign == 0 ? 1 : 0;
allResults.add(new LinkedList<>(results));
}
return allResults;
}
}
class SolutionTest {
public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
List<List<Integer>> ans = new LinkedList<List<Integer>>();
if (root == null) {
return ans;
}
Queue<TreeNode> nodeQueue = new LinkedList<TreeNode>();
nodeQueue.offer(root);
// 关键词 作为 左开头和 右卡头的 标志
boolean isOrderLeft = true;
while (!nodeQueue.isEmpty()) {
Deque<Integer> levelList = new LinkedList<Integer>();
int size = nodeQueue.size();
for (int i = 0; i < size; ++i) {
TreeNode curNode = nodeQueue.poll();
if (curNode.left != null) {
nodeQueue.offer(curNode.left);
}
if (curNode.right != null) {
nodeQueue.offer(curNode.right);
}
if (isOrderLeft) {
levelList.offerLast(curNode.val);
continue;
}
levelList.offerFirst(curNode.val);
}
ans.add(new LinkedList<Integer>(levelList));
isOrderLeft = !isOrderLeft;
}
return ans;
}
}
}