Create 0501-find-mode-in-binary-search-tree.java

Author: benmak11

java/0501-find-mode-in-binary-search-tree.java

@@ -0,0 +1,46 @@
+class Solution {
+    /**
+     * BFS Solution with Runtime Complexity O(n) -> O(n log n)
+     */
+    public int[] findMode(TreeNode root) {
+        if (root == null) return new int[0];
+        List<Integer> curr = new ArrayList<>();
+        Map<Integer, Integer> freqMap = new HashMap<>();
+        Queue<TreeNode> q = new ArrayDeque<>();
+        q.offer(root);
+
+        while (!q.isEmpty()) {
+            int n = q.size();
+            for (int i = 0; i < n; i++) {
+                TreeNode node = q.poll();
+                if (freqMap.containsKey(node.val))
+                    freqMap.put(node.val, freqMap.get(node.val) + 1);
+                else 
+                    freqMap.put(node.val, 1);
+
+                if (node.left != null) q.offer(node.left);
+                if (node.right != null) q.offer(node.right);
+            }
+        }
+
+        int currMax = 0;
+        for (Map.Entry<Integer, Integer> entry : freqMap.entrySet()) {
+            int key = entry.getKey();
+            int value = entry.getValue();
+
+            if (value > currMax) {
+                curr.clear();
+                curr.add(key);
+                currMax = Math.max(currMax, value);
+            } else if (value == currMax){
+                curr.add(key);
+            }
+        }
+
+        int[] res = new int[curr.size()];
+        for (int j = 0; j < curr.size(); j++) {
+            res[j] = curr.get(j);
+        }
+        return res;
+    }
+}