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whai 2024-01-23 22:09:57 +08:00
parent 0d147db2aa
commit 24c2458f4f
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81
src/main/java/cn/whaifree/leetCode/Tree/LeetCode100.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.ArrayDeque;
import java.util.Deque;
import java.util.LinkedList;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/1/23 19:56
* @注释
*/
public class LeetCode100 {
@Test
public void test() {
TreeNode treeNode = TreeNode.constructTree(new Integer[]{1,2,1});
TreeNode treeNode1 = TreeNode.constructTree(new Integer[]{1,1,2});
treeNode1.printTree();
treeNode.printTree();
System.out.println(new Solution1().isSameTree(treeNode, treeNode1));
}
class Solution {
public boolean isSameTree(TreeNode p, TreeNode q) {
if (p == null && q == null) {
return true;
} else if (p == null || q == null) {
return false;
}
// LinkedList能存null
Deque<TreeNode> deque = new LinkedList<>();
deque.add(p);
deque.add(q);
while (!deque.isEmpty()) {
// 防止只剩下一个元素，如果只剩下一个元素，那么一定是false
TreeNode BPop = deque.pop();
TreeNode APop = deque.pop();
if (BPop == null && APop == null) {
// 叶子节点，不需要加入左右子节点
continue;
} else if (BPop != null && APop == null) {
return false;
} else if (BPop == null && APop != null) {
return false;
} else if (BPop.val != APop.val) {
return false;
}
deque.add(BPop.right);
deque.add(APop.right);
deque.add(BPop.left);
deque.add(APop.left);
}
return true;
}
}
class Solution1 {
public boolean isSameTree(TreeNode p, TreeNode q) {
if (p == null && q == null) {
return true;
} else if (p == null && q != null) {
return false;
} else if (p != null && q == null) {
return false;
} else if (p.val != q.val) {
return false;
}
boolean sameTreeRight = isSameTree(p.right, q.right);
boolean sameTreeLeft = isSameTree(p.left, q.left);
return sameTreeLeft && sameTreeRight;
}
}
}

173
src/main/java/cn/whaifree/leetCode/Tree/LeetCode257.java Normal file
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package cn.whaifree.leetCode.Tree;
import cn.whaifree.leetCode.model.Node;
import cn.whaifree.leetCode.model.TreeNode;
import org.junit.Test;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Deque;
import java.util.List;
/**
* @version 1.0
* @Author whai文海
* @Date 2024/1/22 21:54
* @注释
*/
public class LeetCode257 {
@Test
public void test() {
TreeNode root = TreeNode.constructTree(new Integer[]{1, 2, 3, 5,6,7,8,9,0,6});
root.printTree();
System.out.println(new Solution3().binaryTreePaths(root));
}
class Solution {
List<String> res = new ArrayList<String>();
public List<String> binaryTreePaths(TreeNode root) {
if (root == null) {
return res;
}
deal(root, "");
return res;
}
public void deal(TreeNode root, String s) {
if (root == null) return;
if (root.left == null && root.right == null) {
res.add(new StringBuilder(s).append(root.val).toString());
}
String tmp = new StringBuilder(s).append(root.val).append("->").toString();
deal(root.left, tmp);
deal(root.right, tmp);
}
}
class Solution1 {
List<String> res = new ArrayList<String>();
public List<String> binaryTreePaths(TreeNode root) {
if (root == null) {
return res;
}
deal(root, "");
return res;
}
public void deal(TreeNode treeNode, String s) {
if (treeNode==null) return;
//根节点
if (treeNode.right == null && treeNode.left == null) {
res.add(s + treeNode.val);
// res.add(new StringBuilder().append(s).append(treeNode.val).toString());
}
// String tmp = new StringBuilder().append(s).append("->").append(treeNode.val).toString();
String tmp = s + treeNode.val + "->";
deal(treeNode.left, tmp);
deal(treeNode.right, tmp);
}
}
class Solution2 {
List<String> res = new ArrayList<String>();
List<Integer> route = new ArrayList<Integer>();
public List<String> binaryTreePaths(TreeNode root) {
if (root == null) {
return res;
}
deal(root);
return res;
}
public void deal(TreeNode treeNode) {
if (treeNode == null) {
return;
}
route.add(treeNode.val);
if (treeNode.left == null && treeNode.right == null) {
// 根节点
// 可以知道结果了
StringBuilder stringBuilder = new StringBuilder();
int size = route.size();
for (int i = 0; i < size - 1; i++) {
stringBuilder.append(route.get(i)).append("->");
}
stringBuilder.append(route.get(size - 1));
res.add(stringBuilder.toString());
return;
}
if (treeNode.right != null) {
deal(treeNode.right);
// 回溯
route.remove(route.size() - 1);
}
if (treeNode.left != null) {
deal(treeNode.left);
route.remove(route.size() - 1);
}
}
}
class Solution3 {
public List<String> binaryTreePaths(TreeNode root) {
List<String> res = new ArrayList<String>();
if (root == null) {
return res;
}
Deque<Object> stack = new ArrayDeque<>();
stack.add(root);
stack.add(root.val + "");
while (!stack.isEmpty()) {
TreeNode nodePeek = (TreeNode) stack.pop();
String s = (String) stack.pop();
// 叶子节点
if (nodePeek.left == null && nodePeek.right == null) {
// s += "->" + nodePeek.val;
res.add(s);
}
// 左右进栈
if (nodePeek.left != null) {
stack.add(nodePeek.left);
stack.add(new StringBuilder().append(s).append("->").append(nodePeek.left.val).toString());
}
if (nodePeek.right != null) {
stack.add(nodePeek.right);
stack.add(new StringBuilder().append(s).append("->").append(nodePeek.right.val).toString());
}
}
return res;
}
}
}