967. Numbers With Same Consecutive Differences

Difficulty: Medium
92 / 92 test cases passed.
Runtime: 28 ms
Memory Usage: 14.2 MB

Author: YuriSpiridonov

Medium/967.NumbersWithSameConsecutiveDifferences.py

@@ -0,0 +1,50 @@
+"""
+    Return all non-negative integers of length N such that the absolute 
+    difference between every two consecutive digits is K.
+    Note that every number in the answer must not have leading zeros except for 
+    the number 0 itself. For example, 01 has one leading zero and is invalid, 
+    but 0 is valid.
+    You may return the answer in any order.
+
+    Example:
+    Input: N = 3, K = 7
+    Output: [181,292,707,818,929]
+    Explanation: Note that 070 is not a valid number, because it has leading 
+                 zeroes.
+
+    Example:
+    Input: N = 2, K = 1
+    Output: [10,12,21,23,32,34,43,45,54,56,65,67,76,78,87,89,98]
+
+    Note:
+        1. 1 <= N <= 9
+        2. 0 <= K <= 9
+"""
+#Difficulty: Medium
+#92 / 92 test cases passed.
+#Runtime: 28 ms
+#Memory Usage: 14.2 MB
+
+#Runtime: 28 ms, faster than 99.53% of Python3 online submissions for Numbers With Same Consecutive Differences.
+#Memory Usage: 14.2 MB, less than 21.86% of Python3 online submissions for Numbers With Same Consecutive Differences.
+
+class Solution:
+
+    def numsSameConsecDiff(self, N: int, K: int) -> List[int]:
+        self.K = K
+        self.nums = []
+        if N == 1:
+            return [n for n in range(10)]
+        for num in range(1, 10):
+            self.dfs(N-1, num)
+        return self.nums
+
+    def dfs(self, N, num):
+        if N == 0:
+            self.nums.append(num)
+            return
+        digit = num % 10
+        if digit >= self.K:
+            self.dfs(N-1, num*10+digit-self.K)
+        if self.K > 0 and digit + self.K < 10:
+            self.dfs(N-1, num*10+digit+self.K)