Largest Number/ Rotate Array

Author: gavinfish

179 Largest Number.py

@@ -0,0 +1,23 @@
+'''
+Given a list of non negative integers, arrange them such that they form the largest number.
+
+For example, given [3, 30, 34, 5, 9], the largest formed number is 9534330.
+
+Note: The result may be very large, so you need to return a string instead of an integer.
+'''
+
+from functools import cmp_to_key
+
+
+class Solution:
+    # @param {integer[]} nums
+    # @return {string}
+    def largestNumber(self, nums):
+        sorted_nums = sorted(map(str, nums), key=cmp_to_key(lambda x, y: int(y + x) - int(x + y)))
+        result = ''.join(sorted_nums).lstrip('0')
+        return result or '0'
+
+
+if __name__ == "__main__":
+    assert Solution().largestNumber([3, 30, 34, 5, 9]) == '9534330'
+    assert Solution().largestNumber([0, 0]) == '0'

189 Rotate Array.py

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+'''
+Rotate an array of n elements to the right by k steps.
+
+For example, with n = 7 and k = 3, the array [1,2,3,4,5,6,7] is rotated to [5,6,7,1,2,3,4].
+
+Note:
+Try to come up as many solutions as you can, there are at least 3 different ways to solve this problem.
+'''
+
+class Solution(object):
+    def rotate(self, nums, k):
+        """
+        :type nums: List[int]
+        :type k: int
+        :rtype: void Do not return anything, modify nums in-place instead.
+        """
+
+        def reverse(nums, start, end):
+            while start < end:
+                nums[start], nums[end] = nums[end], nums[start]
+                start += 1
+                end -= 1
+
+        n = len(nums)
+        k %= n
+        reverse(nums, 0, n - k - 1)
+        reverse(nums, n - k, n - 1)
+        reverse(nums, 0, n - 1)
+
+
+if __name__ == "__main__":
+    nums = [1, 2, 3, 4, 5, 6, 7]
+    Solution().rotate(nums, 10)
+    assert nums == [5, 6, 7, 1, 2, 3, 4]