Refine

begeekmyfriend · begeekmyfriend · commit 82870a01812d · 2020-06-08T11:33:02.000+08:00
Signed-off-by: begeekmyfriend &lt;begeekmyfriend@gmail.com&gt;
diff --git a/124_binary_tree_maximum_path_sum/bst_max_path.c b/124_binary_tree_maximum_path_sum/bst_max_path.c
@@ -8,35 +8,36 @@ struct TreeNode {
     struct TreeNode *right;
 };
 
-static int partition(struct TreeNode *node, int *max)
+static inline int maximum(int a, int b)
 {
-    int left_max = 0;
-    int right_max = 0;
+    return a > b ? a : b;
+}
 
-    if (node->left != NULL) {
-        left_max = partition(node->left, max);
+static int dfs(struct TreeNode *root, int *max)
+{
+    if (root == NULL) {
+        return 0;
     }
 
-    if (node->right != NULL) {
-        right_max = partition(node->right, max);
-    }
+    /* In case of negative node value */
+    int l = maximum(dfs(root->left, max), 0);
+    int r = maximum(dfs(root->right, max), 0);
 
-    int sum = node->val + left_max + right_max;
+    int sum = root->val + l + r;
     if (sum > *max) {
        *max = sum;
     }
 
-    return node->val + (right_max > left_max ? right_max : left_max);
+    /* The return value does not equal the sum value
+     * since we need to return path through the root node
+     */
+    return root->val + maximum(l, r);
 }
 
 static int maxPathSum(struct TreeNode* root)
 {
-    if (root == NULL) {
-        return 0;
-    }
-
     int max = INT_MIN;
-    partition(root, &max);
+    dfs(root, &max);
     return max;
 }
 
