add 979

Author: cch123

S0979-distribute-coins-in-binary-tree/Cargo.lock

@@ -0,0 +1,8 @@
+[package]
+name = "S0979-distribute-coins-in-binary-tree"
+version = "0.1.0"
+authors = ["xargin <cao1988228@163.com>"]
+edition = "2018"
+
+[dependencies]
+leetcode_prelude="^0.1"

S0979-distribute-coins-in-binary-tree/Cargo.toml

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+struct Solution;
+use leetcode_prelude::*;
+
+// Definition for a binary tree node.
+
+use std::cell::RefCell;
+use std::rc::Rc;
+impl Solution {
+    pub fn distribute_coins(root: Option<Rc<RefCell<TreeNode>>>) -> i32 {
+        let mut res = 0;
+        Solution::dfs(root, &mut res);
+        res
+    }
+
+    pub fn dfs(root: Option<Rc<RefCell<TreeNode>>>, res:&mut i32) -> i32 {
+        if root.is_none() {
+            return 0;
+        }
+
+        let r_u_b = root.as_ref().unwrap().borrow_mut();
+        let left_step_cnt = Solution::dfs(r_u_b.left.clone(), res);
+        let right_step_cnt = Solution::dfs(r_u_b.right.clone(), res);
+        //println!("{}, {}",left_step_cnt, right_step_cnt);
+        *res += left_step_cnt.abs() + right_step_cnt.abs();
+
+        r_u_b.val - 1 + left_step_cnt + right_step_cnt
+    }
+}
+
+fn main() {
+    let r = btree![3,0,0];
+    //println!("{}", Solution::distribute_coins(r));
+    println!("{}", Solution::distribute_coins(btree![1,0,0,null,3]));
+}