Create Smallest String Starting From Leaf.cpp

Author: Its-Aman-Yadav

Medium Problems/Smallest String Starting From Leaf.cpp

@@ -0,0 +1,38 @@
+//https://leetcode.com/problems/smallest-string-starting-from-leaf/description/?envType=daily-question&envId=2024-04-17
+
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    string smallestFromLeaf(TreeNode* root) {
+        string ans;
+        dfs(root, "", ans);
+        return ans;
+    }
+    
+    void dfs(TreeNode* root, string path, string& ans) {
+        if (!root) return;
+        
+        path += char('a' + root->val);
+        
+        if (!root->left && !root->right) {
+            reverse(path.begin(), path.end());
+            if (ans.empty() || path < ans) {
+                ans = path;
+            }
+            reverse(path.begin(), path.end());
+        }
+        
+        dfs(root->left, path, ans);
+        dfs(root->right, path, ans);
+    }
+};