[Tessa1217] Week 10 Solutions

invert-binary-tree/Tessa1217.java

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+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+/**
+ * 이진 트리의 root가 주어질 때 이진 트리를 뒤바꾼 후 root를 반환하세요.
+ */
+class Solution {
+    public TreeNode invertTree(TreeNode root) {
+
+        if (root == null) {
+            return root;
+        }
+
+        TreeNode current = root;
+
+        // 좌우 변경
+        TreeNode temp = current.left;
+        current.left = invertTree(current.right);
+        current.right = invertTree(temp);
+
+        return root;
+    }
+}
+

jump-game/Tessa1217.java

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+class Solution {
+
+    // 시간 복잡도: O(N), 공간복잡도: O(1)
+    public boolean canJump(int[] nums) {
+
+        int maxJump = 0;
+        for (int i = 0; i < nums.length; i++) {
+            // 최대 점프수로 현재 인덱스에 도달할 수 없다면
+            if (i > maxJump) {
+                return false;
+            }
+            maxJump = Math.max(maxJump, i + nums[i]);
+            if (maxJump >= nums.length - 1) {
+                return true;
+            }
+        }
+
+        return true;
+
+    }
+}
+

search-in-rotated-sorted-array/Tessa1217.java

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+class Solution {
+
+    // 이진 탐색: 시간복잡도: O(log n)
+    public int search(int[] nums, int target) {
+
+        int left = 0;
+        int right = nums.length - 1;
+
+        while (left <= right) {
+
+            int mid = left + (right - left)/2;
+
+            if (nums[mid] == target) {
+                return mid;
+            }
+
+            // 구간 설정
+            if (nums[left] <= nums[mid]) {
+                if (nums[left] <= target && target < nums[mid]) {
+                    right = mid - 1;
+                } else {
+                    left = mid + 1;
+                }
+            } else {
+                if (nums[mid] < target && target <= nums[right]) {
+                    left = mid + 1;
+                } else {
+                    right = mid - 1;
+                }
+            }
+        }
+
+        return -1;
+    }
+}