new prolem solved

2023_10_02/maximum-path-sum/src/main.rs

@@ -1,3 +1,41 @@
-fn main() {
-    println!("Hello, world!");
+use std::cmp;
+
+struct Node {
+    data: i32,
+    left: Option<Box<Node>>,
+    right: Option<Box<Node>>,
+}
+
+impl Node {
+    fn new(val: i32) -> Node {
+        Node {
+            data: val,
+            left: None,
+            right: None,
+        }
+    }
+}
+
+fn max_path_sum_util(root: &Option<Box<Node>>, res: &mut i32) -> i32 {
+    match root {
+        Some(node) => {
+            let ls = max_path_sum_util(&node.left, res); // computes the max path sum in the left subtree
+            let rs = max_path_sum_util(&node.right, res); // computes the max path sum in the right subtree
+
+            match (&node.left, &node.right) {
+                (Some(_), Some(_)) => { // if both left and right subtrees are present
+                    *res = cmp::max(*res, ls + rs + node.data); // update the result if needed as the max path sum can be in the left subtree, right subtree or the path can go through the root
+                    cmp::max(ls, rs) + node.data // return the max path sum from the left or right subtree
+                }
+                (None, _) => rs + node.data, // if left subtree is not present, return the max path sum from the right subtree
+                (_, None) => ls + node.data, // if right subtree is not present, return the max path sum from the left subtree
+            }
+        }
+        None => 0, // if the root is None, return 0
+    }
+}
+fn max_path_sum(root: &Option<Box<Node>>) -> i32 { // function to compute the max path sum
+    let mut res = std::i32::MIN; // initialize the result with the minimum value of i32
+    max_path_sum_util(root, &mut res); // call the utility function to compute the max path sum
+    res // return the result
 }