[sm9171] Week 4 solutions

find-minimum-in-rotated-sorted-array/sm9171.java

@@ -0,0 +1,12 @@
+class Solution {
+    public int findMin(int[] nums) {
+        int min = Integer.MAX_VALUE;
+
+        for (int i = 0; i < nums.length; i++) {
+            if (nums[i] < min) {
+                min = nums[i];
+            }
+        }
+        return min;
+    }
+}

maximum-depth-of-binary-tree/sm9171.java

@@ -0,0 +1,10 @@
+class Solution {
+    public int maxDepth(TreeNode root) {
+        if (root == null) {
+            return 0;
+        }
+        int leftDepth = maxDepth(root.left);
+        int rightDepth = maxDepth(root.right);
+        return Math.max(leftDepth, rightDepth) + 1;
+    }
+}

merge-two-sorted-lists/sm9171.java

@@ -0,0 +1,20 @@
+class Solution {
+    public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
+        ListNode dummy = new ListNode(-1);
+        ListNode node = dummy;
+
+        while (list1 != null && list2 != null) {
+            if (list1.val < list2.val) {
+                node.next = list1;
+                list1 = list1.next;
+            } else {
+                node.next = list2;
+                list2 = list2.next;
+            }
+            node = node.next;
+        }
+
+        node.next = list1 != null ? list1 : list2;
+        return dummy.next;
+    }
+}

word-search/sm9171.java

@@ -0,0 +1,42 @@
+class Solution {
+    public boolean exist(char[][] board, String word) {
+        if (board == null || board.length == 0 || word == null || word.length() == 0) {
+            return false;
+        }
+
+        int rows = board.length;
+        int cols = board[0].length;
+        boolean[][] visited = new boolean[rows][cols];
+
+        for (int i = 0; i < rows; i++) {
+            for (int j = 0; j < cols; j++) {
+                if (dfs(board, visited, i, j, word, 0)) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
+    private static boolean dfs(char[][] board, boolean[][] visited, int i, int j, String word, int index) {
+        if (index == word.length()) {
+            return true;
+        }
+
+        if (i < 0 || i >= board.length || j < 0 || j >= board[0].length || visited[i][j] || board[i][j] != word.charAt(index)) {
+            return false;
+        }
+
+
+        visited[i][j] = true;
+
+        boolean found = dfs(board, visited, i + 1, j, word, index + 1) ||
+                dfs(board, visited, i - 1, j, word, index + 1) ||
+                dfs(board, visited, i, j + 1, word, index + 1) ||
+                dfs(board, visited, i, j - 1, word, index + 1);
+
+        visited[i][j] = false;
+
+        return found;
+    }
+}