Binary tree max path sum

Signed-off-by: begeekmyfriend <begeekmyfriend@gmail.com>

Author: begeekmyfriend

124_binary_tree_maximum_path_sum/Makefile

@@ -0,0 +1,2 @@
+all:
+	gcc -O2 -o test bst_max_path.c

124_binary_tree_maximum_path_sum/bst_max_path.c

@@ -0,0 +1,98 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <limits.h>
+
+struct TreeNode {
+    int val;
+    struct TreeNode *left;
+    struct TreeNode *right;
+};
+
+static int recursive(struct TreeNode *node, int *max)
+{
+    int left_max = 0;
+    int right_max = 0;
+
+    if (node->left != NULL) {
+        left_max = recursive(node->left, max);
+    }
+
+    if (node->right != NULL) {
+        right_max = recursive(node->right, max);
+    }
+
+    int sum = node->val + left_max + right_max;
+    if (sum > *max) {
+       *max = sum;
+    }
+
+    int path_sum = node->val + (right_max > left_max ? right_max : left_max);
+    return path_sum > 0 ? path_sum : 0;
+}
+
+static int maxPathSum(struct TreeNode* root)
+{
+    if (root == NULL) {
+        return 0;
+    }
+
+    int max = INT_MIN;
+    recursive(root, &max);
+    return max;
+}
+
+int main(void)
+{
+    struct TreeNode n_1, n_2, n_3, n_4, n_5, n_6, n_7;
+    struct TreeNode n0, n1, n2, n3, n4, n5, n6, n7;
+
+    n_7.val = -7;
+    n_6.val = -6;
+    n_5.val = -5;
+    n_4.val = -4;
+    n_3.val = -3;
+    n_2.val = -2;
+    n_1.val = -1;
+    n0.val  = 0;
+    n1.val  = 1;
+    n2.val  = 2;
+    n3.val  = 3;
+    n4.val  = 4;
+    n5.val  = 5;
+    n6.val  = 6;
+    n7.val  = 7;
+
+    n_7.left  = NULL;
+    n_7.right = NULL;
+    n_6.left  = &n_7;
+    n_6.right = &n_5;
+    n_5.left  = NULL;
+    n_5.right = NULL;
+    n_4.left  = &n_6;
+    n_4.right = &n_2;
+    n_3.left  = NULL;
+    n_3.right = NULL;
+    n_2.left  = &n_3;
+    n_2.right = &n_1;
+    n_1.left  = NULL;
+    n_1.right = NULL;
+    n0.left   = &n_4;
+    n0.right  = &n4;
+    n1.left   = NULL;
+    n1.right  = NULL;
+    n2.left   = &n1;
+    n2.right  = &n3;
+    n3.left   = NULL;
+    n3.right  = NULL;
+    n4.left   = &n2;
+    n4.right  = &n6;
+    n5.left   = NULL;
+    n5.right  = NULL;
+    n6.left   = &n5;
+    n6.right  = &n7;
+    n7.left   = NULL;
+    n7.right  = NULL;
+
+    printf("%d\n", maxPathSum(&n0));
+    return 0;
+}