math

Author: idf

400 Nth Digit.py

@@ -0,0 +1,45 @@
+"""
+Find the nth digit of the infinite integer sequence 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, ...
+
+Note:
+n is positive and will fit within the range of a 32-bit signed integer (n < 231).
+
+Example 1:
+
+Input:
+3
+
+Output:
+3
+Example 2:
+
+Input:
+11
+
+Output:
+0
+
+Explanation:
+The 11th digit of the sequence 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, ... is a 0, which is part of the number 10.
+"""
+__author__ = 'Daniel'
+
+
+class Solution(object):
+    def findNthDigit(self, n):
+        """
+        Math, quotient and remainder
+        :type n: int
+        :rtype: int
+        """
+        digit_cnt = 1
+        num_cnt = 9
+        while n > digit_cnt * num_cnt:
+            n -= digit_cnt * num_cnt
+            digit_cnt += 1
+            num_cnt *= 10
+
+        n -= 1  # debugging: without -1, it just pass over the target digit
+        q, r = n / digit_cnt, n % digit_cnt
+        target = num_cnt / 9 + q
+        return int(str(target)[r])