[feat] Add removeKDigits to make smallest number, insert in bstPreOrder

Author: ravivats

platform-problems/leetcode/may-2020-leetcoding-challenge/13-LeetCode-removeKDigits.py

@@ -21,17 +21,16 @@ def removeKdigits(self, num, k):
             numList = list(num)
             numList.sort()
             return numList[0]
-        totalRemoved = 0
-        numClone = num
-        for i in range(len(num) - 1):
-            if num[i] > num[i + 1]:
-                numClone = numClone.replace(num[i], '', 1)
-                totalRemoved += 1
-                if totalRemoved == k:
-                    break
-        return removeZeros(numClone[:len(numClone) - k + totalRemoved])
+
+        for j in range(k):
+            i = 0
+            while i + 1 < len(num) and num[i] <= num[i + 1]:
+                i += 1
+            # remove the character
+            num = num[:i] + num[i + 1:]
+        return removeZeros(num)
 
 
 if __name__ == '__main__':
     s = Solution()
-    print(s.removeKdigits("1234567890", 9))
+    print(s.removeKdigits("122519", 3))

platform-problems/leetcode/may-2020-leetcoding-challenge/24-LeetCode-bstFromPreorder.py

@@ -0,0 +1,45 @@
+'''
+Return the root node of a binary search tree that matches the given preorder traversal.
+
+(Recall that a binary search tree is a binary tree where for every node, any descendant of node.
+left has a value < node.val, and any descendant of node.right has a value > node.val.  
+Also recall that a preorder traversal displays the value of the node first, 
+then traverses node.left, then traverses node.right.)
+
+It's guaranteed that for the given test cases there is always possible to find a 
+binary search tree with the given requirements.
+
+Example 1: Input: [8,5,1,7,10,12], Output: [8,5,10,1,7,null,12]
+'''
+import math
+
+# Definition for a binary tree node.
+# class TreeNode(object):
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+
+
+def insertInBst(root, val):
+    if root == None:
+        root = TreeNode()
+        root.val = val
+        return root
+    if val < root.val:
+        root.left = insertInBst(root.left, val)
+    if val > root.val:
+        root.right = insertInBst(root.right, val)
+    return root
+
+
+class Solution(object):
+    def bstFromPreorder(self, preorder):
+        """
+        :type preorder: List[int]
+        :rtype: TreeNode
+        """
+        root = None
+        for i in range(len(preorder)):
+            root = insertInBst(root, preorder[i])
+        return root