diff --git a/container-with-most-water/TonyKim9401.java b/container-with-most-water/TonyKim9401.java
new file mode 100644
index 00000000..e3a24492
--- /dev/null
+++ b/container-with-most-water/TonyKim9401.java
@@ -0,0 +1,24 @@
+// TC:
+// SC:
+class Solution {
+    public int maxArea(int[] height) {
+        int max = 0;
+
+        int start = 0;
+        int end = height.length-1;
+
+        while (start < end) {
+            int heightLeft = height[start];
+            int heightRight = height[end];
+
+            int hei = Math.min(heightLeft, heightRight);
+            int wid = end - start;
+
+            max = Math.max(max, hei*wid);
+
+            if (heightRight > heightLeft) start += 1;
+            else end -= 1;
+        }
+        return max;
+    }
+}
diff --git a/design-add-and-search-words-data-structure/TonyKim9401.java b/design-add-and-search-words-data-structure/TonyKim9401.java
new file mode 100644
index 00000000..ed3f0986
--- /dev/null
+++ b/design-add-and-search-words-data-structure/TonyKim9401.java
@@ -0,0 +1,56 @@
+// SC: O(n)
+// -> n is the length of the given String
+// TC: O(n * 26)
+// -> n is the length of the given String * the number of alphabets
+class TrieNode {
+    TrieNode[] childNode;
+    boolean isEndOfWord;
+
+    public TrieNode() {
+        childNode = new TrieNode[26];
+        isEndOfWord = false;
+    }
+}
+
+class WordDictionary {
+
+    private TrieNode root;
+
+    public WordDictionary() {
+        root = new TrieNode();
+    }
+
+    public void addWord(String word) {
+        TrieNode node = root;
+
+        for (char c : word.toCharArray()) {
+            int idx = c - 'a';
+            if (node.childNode[idx] == null) {
+                node.childNode[idx] = new TrieNode();
+            }
+            node = node.childNode[idx];
+        }
+        node.isEndOfWord = true;
+    }
+
+    public boolean search(String word) {
+        return searchInNode(word.toCharArray(), 0, root);
+    }
+
+    private boolean searchInNode(char[] word, int idx, TrieNode node) {
+        if (idx == word.length) return node.isEndOfWord;
+
+        char c = word[idx];
+
+        if (c == '.') {
+            for (TrieNode child : node.childNode) {
+                if (child != null && searchInNode(word, idx+1, child)) return true;
+            }
+            return false;
+        } else {
+            int childIdx = c - 'a';
+            if (node.childNode[childIdx] == null) return false;
+            return searchInNode(word, idx+1, node.childNode[childIdx]);
+        }
+    }
+}
diff --git a/longest-increasing-subsequence/TonyKim9401.java b/longest-increasing-subsequence/TonyKim9401.java
new file mode 100644
index 00000000..e26083a9
--- /dev/null
+++ b/longest-increasing-subsequence/TonyKim9401.java
@@ -0,0 +1,22 @@
+// TC: O(n log n)
+// -> nums for loop O(n) + binarySearch O(log n)
+// SC: O(n)
+// -> ArrayList could have nums all elements
+class Solution {
+    public int lengthOfLIS(int[] nums) {
+        List<Integer> output = new ArrayList<>();
+
+        for (int num : nums) {
+            int start = 0;
+            int end = output.size();
+            while (start < end) {
+                int mid = start + (end - start) / 2;
+                if (output.get(mid) < num) start = mid + 1;
+                else end = mid;
+            }
+            if (start == output.size()) output.add(num);
+            else output.set(start, num);
+        }
+        return output.size();
+    }
+}
diff --git a/spiral-matrix/TonyKim9401.java b/spiral-matrix/TonyKim9401.java
new file mode 100644
index 00000000..9f36f50a
--- /dev/null
+++ b/spiral-matrix/TonyKim9401.java
@@ -0,0 +1,44 @@
+class Solution {
+    public List<Integer> spiralOrder(int[][] matrix) {
+        List<Integer> output = new ArrayList<>();
+        int north = 0;
+        int south = matrix.length - 1;
+        int east = matrix[0].length - 1;
+        int west = 0;
+
+        while (north <= south && west <= east) {
+            int j = west;
+            while (j <= east) {
+                output.add(matrix[north][j]);
+                j += 1;
+            }
+            north += 1;
+
+            int i = north;
+            while (i <= south) {
+                output.add(matrix[i][east]);
+                i += 1;
+            }
+            east -= 1;
+
+            if (north <= south) {
+                j = east;
+                while (j >= west) {
+                    output.add(matrix[south][j]);
+                    j -= 1;
+                }
+                south -= 1;
+            }
+
+            if (west <= east) {
+                i = south;
+                while (i >= north) {
+                    output.add(matrix[i][west]);
+                    i -= 1;
+                }
+                west += 1;
+            }
+        }
+        return output;
+    }
+}
diff --git a/valid-parentheses/TonyKim9401.java b/valid-parentheses/TonyKim9401.java
new file mode 100644
index 00000000..c3c88b54
--- /dev/null
+++ b/valid-parentheses/TonyKim9401.java
@@ -0,0 +1,18 @@
+// TC: O(n)
+// -> n = s.length
+// SC: O(n)
+// -> n = s.length / 2
+class Solution {
+    public boolean isValid(String s) {
+        Stack<Character> stack = new Stack<>();
+
+        for (char c : s.toCharArray()) {
+            if (c == '(') stack.add(')');
+            else if (c == '{') stack.add('}');
+            else if (c == '[') stack.add(']');
+            else if (stack.isEmpty() || stack.pop() != c) return false;
+        }
+
+        return stack.isEmpty();
+    }
+}