Dec 24

Author: GSNCodes

December_LeetCode_Challenge/Next_Greater_Element_III.py

@@ -0,0 +1,55 @@
+Given a positive integer n, find the smallest integer which has 
+exactly the same digits existing in the integer n and is greater in value than n. 
+If no such positive integer exists, return -1.
+
+Note that the returned integer should fit in 32-bit integer, 
+if there is a valid answer but it does not fit in 32-bit integer, return -1.
+
+Example 1:
+Input: n = 12
+Output: 21
+
+Example 2:
+Input: n = 21
+Output: -1
+ 
+Constraints:
+1 <= n <= 231 - 1
+
+
+# O(n) Time and O(1) Space
+class Solution:
+    def nextGreaterElement(self, n: int) -> int:
+        
+        digit_count = [0 for i in range(10)]
+        
+        current_digit = -1
+        prev_digit = -1
+        
+        while n > 0:
+            
+            current_digit = n % 10
+            n = n//10
+            digit_count[current_digit] += 1
+            
+            if prev_digit > current_digit:
+                
+                digit = current_digit + 1
+                
+                while digit_count[digit] == 0:
+                    digit += 1
+                
+                digit_count[digit] -= 1
+                
+                n = n*10 + digit
+                
+                for i in range(10):
+                    while digit_count[i] > 0:
+                        n = n*10 + i
+                        digit_count[i] -= 1
+                
+                return n if n<(2**31)-1 else -1
+            
+            prev_digit = current_digit
+            
+        return -1