MinimumDepthOfBinaryTree111

Author: fluency03

README.md

@@ -40,11 +40,11 @@
 
 
 
-# Total: 238
+# Total: 239
 
 | Easy |  Medium | Hard | - |
 |:----:|:-------:|:----:|:-:|
-|  58  |   137   |  41  | 2 |
+|  59  |   137   |  41  | 2 |
 
 
 | Question | Solution | Difficulty |
@@ -130,6 +130,7 @@
 | [108. Convert Sorted Array to Binary Search Tree](https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/ConvertSortedArrayToBinarySearchTree108.java) | Easy |
 | [109. Convert Sorted List to Binary Search Tree](https://leetcode.com/problems/convert-sorted-list-to-binary-search-tree/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/ConvertSortedListToBST109.java) | Medium |
 | [110. Balanced Binary Tree](https://leetcode.com/problems/balanced-binary-tree/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/BalancedBinaryTree110.java) | Easy |
+| [111. Minimum Depth of Binary Tree](https://leetcode.com/problems/minimum-depth-of-binary-tree/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/MinimumDepthOfBinaryTree111.java) | Easy |
 | [112. Path Sum](https://leetcode.com/problems/path-sum/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/PathSum112.java) | Easy |
 | [114. Flatten Binary Tree to Linked List](https://leetcode.com/problems/flatten-binary-tree-to-linked-list/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/FlattenBinaryTreeToLinkedList114.java) | Medium |
 | [116. Populating Next Right Pointers in Each Node](https://leetcode.com/problems/populating-next-right-pointers-in-each-node/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/PopulatingNextRightPointersInEachNode116.java) | Medium |

src/MinimumDepthOfBinaryTree111.java

@@ -0,0 +1,58 @@
+/**
+ * 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:
+ * 
+ * Given binary tree [3,9,20,null,null,15,7],
+ * 
+ *     3
+ *    / \
+ *   9  20
+ *     /  \
+ *    15   7
+ * return its minimum depth = 2.
+ * 
+ */
+
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+
+public class MinimumDepthOfBinaryTree111 {
+    public int minDepth(TreeNode root) {
+        if (root == null) return 0;
+        Queue<TreeNode> q = new LinkedList<>();
+        int depth = 1;
+        q.add(root);
+        while (!q.isEmpty()) {
+            int size = q.size();
+            for (int i=0; i<size; i++) {
+                TreeNode node = q.remove();
+                boolean isLeaf = true;
+                if (node.left != null) {
+                    isLeaf = false;
+                    q.add(node.left);
+                }
+                if (node.right != null) {
+                    isLeaf = false;
+                    q.add(node.right);
+                }
+                if (isLeaf) return depth;
+            }
+            depth++;
+        }
+        return depth;
+    }
+    
+}