[juhui-jeong] WEEK 13 solutions

lowest-common-ancestor-of-a-binary-search-tree/juhui-jeong.java

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+/*
+    시간복잡도: O(log N)
+    공간복잡도: O(1)
+ */
+class Solution {
+    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
+        while(root != null) {
+            if (p.val < root.val && q.val < root.val) {
+                root = root.left;
+            } else if (p.val > root.val && q.val > root.val) {
+                root = root.right;
+            } else {
+                return root;
+            }
+        }
+        return null;
+    }
+}

meeting-rooms/juhui-jeong.java

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+/**
+ * Definition of Interval:
+ * public class Interval {
+ *     public int start, end;
+ *     public Interval(int start, int end) {
+ *         this.start = start;
+ *         this.end = end;
+ *     }
+ * }
+ */
+
+class Solution {
+    public boolean canAttendMeetings(List<Interval> intervals) {
+        intervals.sort((a, b) -> {
+            if (a.start != b.start) return Integer.compare(a.start, b.start);
+            return Integer.compare(a.end, b.end);
+        });
+
+        for (int i = 1; i < intervals.size(); i++) {
+            if (intervals.get(i-1).end > intervals.get(i).start) {
+                return false;
+            }
+        }
+        return true;
+    }
+}