Trees: Binary Tree Max Path Sum

src/main/java/com/pallamsetty/trees/BinaryTreeMaxPathSum.java

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+package com.pallamsetty.trees;
+
+/*
+* Leetcode 124
+* */
+
+import com.pallamsetty.trees.helpers.TreeNode;
+
+public class BinaryTreeMaxPathSum {
+    public int getMaxSum(TreeNode root) {
+        int[] res = new int[] { root.val };
+
+        dfs(root, res);
+        return res[0];
+    }
+
+    private int dfs(TreeNode root, int[] res) {
+        if(root == null) {
+            return 0;
+        }
+
+        int leftMax = Math.max(dfs(root.left, res), 0);
+        int rightMax = Math.max(dfs(root.right, res), 0);
+
+        res[0] = Math.max(res[0], root.val + leftMax + rightMax);
+        return root.val + Math.max(leftMax, rightMax);
+    }
+}

src/test/java/com/pallamsetty/trees/BinaryTreeMaxPathSumTest.java

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+package com.pallamsetty.trees;
+
+import com.pallamsetty.trees.helpers.TreeNode;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class BinaryTreeMaxPathSumTest {
+    private final BinaryTreeMaxPathSum btmps;
+
+    public BinaryTreeMaxPathSumTest() {
+        btmps = new BinaryTreeMaxPathSum();
+    }
+
+    @Test
+    public void testGetMaxPathSum1() {
+        TreeNode root = new TreeNode(1);
+        root.left = new TreeNode(2);
+        root.right = new TreeNode(3);
+
+        assertEquals(6, btmps.getMaxSum(root));
+    }
+
+    @Test
+    public void testGetMaxPathSum2() {
+        TreeNode root = new TreeNode(-15);
+        root.left = new TreeNode(10);
+        root.right = new TreeNode(20);
+        root.right.left = new TreeNode(15);
+        root.right.left.left = new TreeNode(-5);
+        root.right.right = new TreeNode(5);
+
+        assertEquals(40, btmps.getMaxSum(root));
+    }
+}