feat:add Solution.cpp for 0111. Minimum Depth of Binary Tree

Author: Stackingrule

solution/0100-0199/0111.Minimum Depth of Binary Tree/Solution.cpp

@@ -0,0 +1,9 @@
+class Solution {
+public:
+    int minDepth(TreeNode* root) {
+        if (!root) return 0;
+        if (!root->left) return 1 + minDepth(root->right);
+        if (!root->right) return 1 + minDepth(root->left);
+        return 1 + min(minDepth(root->left), minDepth(root->right));
+    }
+};