'Minimum Depth of Binary Tree' soln

Author: joewnga

README.md

@@ -116,8 +116,8 @@ Note: Some solutions have multiple approaches implemented
 | 108 | [Convert Sorted Array to Binary Search Tree](https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/) | [Solution](./leetcode/convert_sorted_array_to_bst.rs) | Easy |
 | 109 | [Convert Sorted List to Binary Search Tree](https://leetcode.com/problems/convert-sorted-list-to-binary-search-tree/) | [Solution](./leetcode/convert_sorted_list_to_bst.rs) | Medium |
 | 110 | [Balanced Binary Tree](https://leetcode.com/problems/balanced-binary-tree/) | [Solution](./leetcode/balanced_binary_tree.rs) | Easy |
-| >111 | [Minimum Depth of Binary Tree](https://leetcode.com/problems/minimum-depth-of-binary-tree/) | [Solution](./leetcode/minimum_depth_of_binary_tree.rs) | Easy |
-| 112 | [Path Sum](https://leetcode.com/problems/path-sum/) | [Solution](./leetcode/path_sum.rs) | Easy |
+| 111 | [Minimum Depth of Binary Tree](https://leetcode.com/problems/minimum-depth-of-binary-tree/) | [Solution](./leetcode/minimum_depth_of_binary_tree.rs) | Easy |
+| >112 | [Path Sum](https://leetcode.com/problems/path-sum/) | [Solution](./leetcode/path_sum.rs) | Easy |
 | 113 | [Path Sum II](https://leetcode.com/problems/path-sum-ii/) | [Solution](./leetcode/path_sum_ii.rs) | Medium |
 | 114 | [Flatten Binary Tree to Linked List](https://leetcode.com/problems/flatten-binary-tree-to-linked-list/) | [Solution](./leetcode/flatten_binary_tree.rs) | Medium |
 | 115 | [Distinct Subsequences](https://leetcode.com/problems/distinct-subsequences/) | [Solution](./leetcode/distinct_subsequences.rs) | Hard |

leetcode/minimum_depth_of_binary_tree.rs

@@ -0,0 +1,73 @@
+/// 
+/// Problem: Minimum Depth of Binary Tree
+/// 
+/// Given a binary tree, find its minimum depth.
+/// 
+/// The minimum depth is the number of nodes along the shortest path from the root node 
+/// down to the nearest leaf node.
+/// 
+/// Note: A leaf is a node with no children.
+/// 
+/// Example 1:
+/// Input: root = [3,9,20,null,null,15,7]
+/// Output: 2
+/// 
+/// Example 2:
+/// Input: root = [2,null,3,null,4,null,5,null,6]
+/// Output: 5
+/// 
+/// Constraints:
+/// The number of nodes in the tree is in the range [0, 10^5].
+/// -1000 <= Node.val <= 1000
+/// 
+
+// Definition for a binary tree node (provided by LeetCode)
+// #[derive(Debug, PartialEq, Eq)]
+// pub struct TreeNode {
+//   pub val: i32,
+//   pub left: Option<Rc<RefCell<TreeNode>>>,
+//   pub right: Option<Rc<RefCell<TreeNode>>>,
+// }
+// 
+// impl TreeNode {
+//   #[inline]
+//   pub fn new(val: i32) -> Self {
+//     TreeNode {
+//       val,
+//       left: None,
+//       right: None
+//     }
+//   }
+// }
+
+// # Solution
+// Time complexity: O(n) 
+// Space complexity: O(h) Where h is the height of the tree (for the recursion stack)
+
+
+use std::rc::Rc;
+use std::cell::RefCell;
+use std::cmp;
+impl Solution {
+    pub fn min_depth(root: Option<Rc<RefCell<TreeNode>>>) -> i32 {
+         match root {
+           None => 0,
+           Some(node) => {
+               let node_ref = node.borrow();
+               let left_depth = Self::min_depth(node_ref.left.clone());
+               let right_depth = Self::min_depth(node_ref.right.clone());
+               
+               
+               if left_depth == 0 {
+                   return right_depth + 1;
+               }
+               if right_depth == 0 {
+                   return left_depth + 1;
+               }
+               
+               
+               1 + cmp::min(left_depth, right_depth)
+           }
+       }
+    }
+}