[s0ooo0k] WEEK 04 solutions

find-minimum-in-rotated-sorted-array/s0ooo0k.java

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+class Solution {
+    /*
+     * 시간복잡도 O(log n)
+     */
+    public int findMin(int[] nums) {
+        int left = 0;
+        int right = nums.length-1;
+
+        while(left<right) {
+            int mid =(right - left)/2+left;
+            if(nums[right]<nums[mid]) {
+                left=mid+1;
+            }
+            else right=mid;
+        }
+        return nums[left];
+    }
+}
+

maximum-depth-of-binary-tree/s0ooo0k.java

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+class Solution {
+    /*
+     * 시간복잡도: O(n)
+     */
+    public int maxDepth(TreeNode root) {
+        if(root==null) return 0;
+        return 1+Math.max(maxDepth(root.left), maxDepth(root.right));
+    }
+}
+

merge-two-sorted-lists/s0ooo0k.java

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+class Solution {
+    /*
+     * 시간복잡도 O(m+n) m: list1의 길이, n: list2의 길이
+     */
+    public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
+        if(list1==null) return list2;
+        if(list2==null) return list1;
+
+        if(list1.val <= list2.val) {
+            list1.next = mergeTwoLists(list1.next, list2);
+            return list1;
+        }
+        else {/*  */
+            list2.next = mergeTwoLists(list1, list2.next);
+            return list2;
+        }
+    }
+}
+