feat(leetcode): add No.1161

Author: mickey0524

1161.Maximum-Level-Sum-of-a-Binary-Tree.java

@@ -0,0 +1,49 @@
+// https://leetcode.com/problems/maximum-level-sum-of-a-binary-tree/
+//
+// algorithms
+// Easy (72.24%)
+// Total Accepted: 3,412
+// Total Submissions: 4,723
+// beats 100.0% of java submissions
+
+/**
+ * Definition for a binary tree node. public class TreeNode { int val; TreeNode
+ * left; TreeNode right; TreeNode(int x) { val = x; } }
+ */
+class Solution {
+    public int maxLevelSum(TreeNode root) {
+        LinkedList<TreeNode> q = new LinkedList<>();
+        q.offer(root);
+        q.offer(null);
+
+        int levelSum = 0, maxSum = Integer.MIN_VALUE;
+        int level = 1, res = 1;
+
+        while (true) {
+            TreeNode curNode = q.pollFirst();
+            if (curNode == null) {
+                if (levelSum > maxSum) {
+                    maxSum = levelSum;
+                    res = level;
+                }
+                if (q.size() == 0) {
+                    break;
+                }
+                q.offer(null);
+                levelSum = 0;
+                level++;
+            } else {
+                levelSum += curNode.val;
+                if (curNode.left != null) {
+                    q.offer(curNode.left);
+                }
+
+                if (curNode.right != null) {
+                    q.offer(curNode.right);
+                }
+            }
+        }
+
+        return res;
+    }
+}