add 1161

Author: fishercoder1534

README.md

@@ -59,6 +59,7 @@ _If you like this project, please leave me a star._ ★
 |1176|[Diet Plan Performance](https://leetcode.com/problems/diet-plan-performance/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1176.java) | |Easy|Array, Sliding Window|
 |1175|[Prime Arrangements](https://leetcode.com/problems/prime-arrangements/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1175.java) | |Easy||
 |1165|[Single-Row Keyboard](https://leetcode.com/problems/single-row-keyboard/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1165.java) | |Easy||
+|1161|[Maximum Level Sum of a Binary Tree](https://leetcode.com/problems/maximum-level-sum-of-a-binary-tree/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1161.java) | |Medium|Graph|
 |1160|[Find Words That Can Be Formed by Characters](https://leetcode.com/problems/find-words-that-can-be-formed-by-characters/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1160.java)| |Easy||
 |1154|[Day of the Year](https://leetcode.com/problems/day-of-the-year/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1154.java) | |Easy||
 |1150|[Check If a Number Is Majority Element in a Sorted Array](https://leetcode.com/problems/check-if-a-number-is-majority-element-in-a-sorted-array/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1150.java)|[:tv:](https://youtu.be/-t2cdVs9cKk) |Easy||

src/main/java/com/fishercoder/solutions/_1161.java

@@ -0,0 +1,64 @@
+package com.fishercoder.solutions;
+
+import com.fishercoder.common.classes.TreeNode;
+
+import java.util.LinkedList;
+import java.util.Queue;
+import java.util.TreeMap;
+
+/**
+ * 1161. Maximum Level Sum of a Binary Tree
+ *
+ * Given the root of a binary tree, the level of its root is 1, the level of its children is 2, and so on.
+ * Return the smallest level X such that the sum of all the values of nodes at level X is maximal.
+ *
+ * Example 1:
+ *          1
+ *         / \
+ *        7  0
+ *       / \
+ *      7  -8
+ *
+ * Input: [1,7,0,7,-8,null,null]
+ * Output: 2
+ *
+ * Explanation:
+ * Level 1 sum = 1.
+ * Level 2 sum = 7 + 0 = 7.
+ * Level 3 sum = 7 + -8 = -1.
+ * So we return the level with the maximum sum which is level 2.
+ *
+ * Note:
+ * The number of nodes in the given tree is between 1 and 10^4.
+ * -10^5 <= node.val <= 10^5
+ * */
+public class _1161 {
+    public static class Solution1 {
+        public int maxLevelSum(TreeNode root) {
+            if (root == null) {
+                return 0;
+            }
+            Queue<TreeNode> q = new LinkedList<>();
+            q.offer(root);
+            TreeMap<Integer, Integer> treeMap = new TreeMap<>((a, b) -> b - a);
+            int level = 1;
+            while (!q.isEmpty()) {
+                int size = q.size();
+                int sum = 0;
+                for (int i = 0; i < size; i++) {
+                    TreeNode curr = q.poll();
+                    sum += curr.val;
+                    if (curr.left != null) {
+                        q.offer(curr.left);
+                    }
+                    if (curr.right != null) {
+                        q.offer(curr.right);
+                    }
+                }
+                treeMap.put(sum, level);
+                level++;
+            }
+            return treeMap.firstEntry().getValue();
+        }
+    }
+}

src/test/java/com/fishercoder/_1161Test.java

@@ -0,0 +1,26 @@
+package com.fishercoder;
+
+import com.fishercoder.common.classes.TreeNode;
+import com.fishercoder.common.utils.TreeUtils;
+import com.fishercoder.solutions._1161;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.Arrays;
+
+import static junit.framework.Assert.assertEquals;
+
+public class _1161Test {
+    private static _1161.Solution1 solution1;
+
+    @BeforeClass
+    public static void setup() {
+        solution1 = new _1161.Solution1();
+    }
+
+    @Test
+    public void test1() {
+        TreeNode root = TreeUtils.constructBinaryTree(Arrays.asList(1, 7, 0, 7, -8, null, null));
+        assertEquals(2, solution1.maxLevelSum(root));
+    }
+}