From 5f4e52a437390d538182a8a8c91944775a7f4604 Mon Sep 17 00:00:00 2001
From: ktony <k.tony9412@gmail.com>
Date: Tue, 19 Nov 2024 21:26:20 -0500
Subject: [PATCH 1/5] Subtree Of Another Tree
---
subtree-of-another-tree/TonyKim9401.java | 25 ++++++++++++++++++++++++
1 file changed, 25 insertions(+)
create mode 100644 subtree-of-another-tree/TonyKim9401.java
diff --git a/subtree-of-another-tree/TonyKim9401.java b/subtree-of-another-tree/TonyKim9401.java
new file mode 100644
index 000000000..0556bb3e2
--- /dev/null
+++ b/subtree-of-another-tree/TonyKim9401.java
@@ -0,0 +1,25 @@
+// TC: O(n)
+// need to check all nodes in the worst case
+// SC: O(n)
+// recursion requires O(n) SC in the worst case
+class Solution {
+ public boolean isSubtree(TreeNode root, TreeNode subRoot) {
+ if (root == null) return false;
+
+ if (sameCheck(root, subRoot)) return true;
+
+ return isSubtree(root.left, subRoot) ||
+ isSubtree(root.right, subRoot);
+ }
+
+ private boolean sameCheck(TreeNode root, TreeNode subRoot) {
+ if (root == null || subRoot == null) {
+ return root == null && subRoot == null;
+ }
+
+ if (root.val != subRoot.val) return false;
+
+ return sameCheck(root.left, subRoot.left) &&
+ sameCheck(root.right, subRoot.right);
+ }
+}
From 06d77e2fb127a9c03fd405a5b50207917aa663e3 Mon Sep 17 00:00:00 2001
From: ktony <k.tony9412@gmail.com>
Date: Wed, 20 Nov 2024 17:00:08 -0500
Subject: [PATCH 2/5] Validate Binary Search Tree
---
validate-binary-search-tree/TonyKim9401.java | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
create mode 100644 validate-binary-search-tree/TonyKim9401.java
diff --git a/validate-binary-search-tree/TonyKim9401.java b/validate-binary-search-tree/TonyKim9401.java
new file mode 100644
index 000000000..0eb18e48b
--- /dev/null
+++ b/validate-binary-search-tree/TonyKim9401.java
@@ -0,0 +1,17 @@
+// TC: O(n)
+// visit all nodes to compare
+// SC: O(n)
+// recursion requires O(n) SC in the worst case
+class Solution {
+ public boolean isValidBST(TreeNode root) {
+ return dfs(root, Long.MIN_VALUE, Long.MAX_VALUE);
+ }
+
+ private boolean dfs(TreeNode node, long min, long max) {
+ if (node == null) return true;
+
+ if (node.val <= min || node.val >= max) return false;
+ return dfs(node.left, min, node.val) &&
+ dfs(node.right, node.val, max);
+ }
+}
From 1f134cd34ff5c154a8f1b649df463f2216be7414 Mon Sep 17 00:00:00 2001
From: ktony <k.tony9412@gmail.com>
Date: Wed, 20 Nov 2024 17:00:23 -0500
Subject: [PATCH 3/5] Longest Palindromic Substring
---
.../TonyKim9401.java | 31 +++++++++++++++++++
1 file changed, 31 insertions(+)
create mode 100644 longest-palindromic-substring/TonyKim9401.java
diff --git a/longest-palindromic-substring/TonyKim9401.java b/longest-palindromic-substring/TonyKim9401.java
new file mode 100644
index 000000000..3bb2f9183
--- /dev/null
+++ b/longest-palindromic-substring/TonyKim9401.java
@@ -0,0 +1,31 @@
+// TC: O(n^2)
+// for loop & nested while loop => total O(n^2)
+// SC: O(1)
+// uses only constant space => O(1)
+class Solution {
+ public String longestPalindrome(String s) {
+ int right = 0;
+ int left = 0;
+
+ for (int i = 0; i < s.length(); i++) {
+ int even = pad(s, i, i);
+ int odd = pad(s, i, i+1);
+ int max = Math.max(even, odd);
+
+ if (max > (right - left)) {
+ right = i + (max + 1) / 2;
+ left = i - max / 2;
+ }
+ }
+
+ return s.substring(left, right+1);
+ }
+
+ private int pad(String s, int start, int end) {
+ while (start >= 0 && end < s.length() && s.charAt(start) == s.charAt(end)) {
+ start -= 1;
+ end += 1;
+ }
+ return start - end;
+ }
+}
From 596556f72dce9bc4397ce2741a6e11ca0c2116c4 Mon Sep 17 00:00:00 2001
From: ktony <k.tony9412@gmail.com>
Date: Thu, 21 Nov 2024 23:14:51 -0500
Subject: [PATCH 4/5] Rotate Image
---
rotate-image/TonyKim9401.java | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
create mode 100644 rotate-image/TonyKim9401.java
diff --git a/rotate-image/TonyKim9401.java b/rotate-image/TonyKim9401.java
new file mode 100644
index 000000000..cf7d43208
--- /dev/null
+++ b/rotate-image/TonyKim9401.java
@@ -0,0 +1,19 @@
+// TC: O(n^2)
+// visit all elements with nested for-loop
+// SC: O(1)
+// constant space complexity
+class Solution {
+ public void rotate(int[][] matrix) {
+ int n = matrix.length;
+
+ for (int i = 0; i < (n + 1) / 2; i++) {
+ for (int j = 0; j < n / 2; j++) {
+ int temp = matrix[n-1-j][i];
+ matrix[n-1-j][i] = matrix[n-1-i][n-1-j];
+ matrix[n-1-i][n-1-j] = matrix[j][n-1-i];
+ matrix[j][n-1-i] = matrix[i][j];
+ matrix[i][j] = temp;
+ }
+ }
+ }
+}
From 9c14f52aef1d13a67943c65a09808d16ccb7b925 Mon Sep 17 00:00:00 2001
From: ktony <k.tony9412@gmail.com>
Date: Fri, 22 Nov 2024 13:26:41 -0500
Subject: [PATCH 5/5] Subtree Of Another Tree TC, SC re-calculation
---
subtree-of-another-tree/TonyKim9401.java | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/subtree-of-another-tree/TonyKim9401.java b/subtree-of-another-tree/TonyKim9401.java
index 0556bb3e2..769be930d 100644
--- a/subtree-of-another-tree/TonyKim9401.java
+++ b/subtree-of-another-tree/TonyKim9401.java
@@ -1,7 +1,7 @@
-// TC: O(n)
-// need to check all nodes in the worst case
-// SC: O(n)
-// recursion requires O(n) SC in the worst case
+// TC: O(n * m)
+// need to check all nodes and subRoot nodes in the worst case
+// SC: O(h1 + h2)
+// the high of root = h1 + the high of subRoot h2 => O(h1 + h2)
class Solution {
public boolean isSubtree(TreeNode root, TreeNode subRoot) {
if (root == null) return false;