solve binary tree maximum path sum

Author: sora0319

binary-tree-maximum-path-sum/sora0319.java

@@ -0,0 +1,23 @@
+public class Solution {
+    private int maxSum;
+
+    public int maxPathSum(TreeNode root) {
+        maxSum = root.val;
+        dfs(root);
+        return maxSum;
+    }
+
+    private int dfs(TreeNode node) {
+        if (node == null) {
+            return 0;
+        }
+
+        int leftMax = Math.max(dfs(node.left), 0);
+        int rightMax = Math.max(dfs(node.right), 0);
+
+        maxSum = Math.max(maxSum, node.val + leftMax + rightMax);
+
+        return node.val + Math.max(leftMax, rightMax);
+    }
+}
+