AC

Author: elfxwt

Binary-Tree/Convert Sorted Array to Binary Search Tree

@@ -0,0 +1,25 @@
+//递归思想很好做~注意返回空
+
+class Solution {
+	TreeNode * dfs(int start,int end,vector<int> &num)
+	{
+			if(start <= end)
+			{
+				int mid = (start + end) / 2;
+				TreeNode *newNode = new TreeNode(num[mid]);
+				newNode->left = dfs(start,mid - 1,num);
+				newNode->right = dfs(mid + 1,end,num);
+				return newNode;
+			}
+			else
+				return NULL;
+	}
+
+public:
+    TreeNode *sortedArrayToBST(vector<int> &num) {
+		if(num.size() < 1)
+			return nullptr;
+		return dfs(0,num.size()-1,num);
+        
+    }
+};