Create continuous-subarray-sum.py

Author: kamyu104

Python/continuous-subarray-sum.py

@@ -0,0 +1,40 @@
+# Time:  O(n)
+# Space: O(k)
+
+# Given a list of non-negative numbers and a target integer k,
+# write a function to check if the array has a continuous subarray
+# of size at least 2 that sums up to the multiple of k, that is,
+# sums up to n*k where n is also an integer.
+#
+# Example 1:
+# Input: [23, 2, 4, 6, 7],  k=6
+# Output: True
+# Explanation: Because [2, 4] is a continuous subarray of size 2 and sums up to 6.
+# Example 2:
+# Input: [23, 2, 6, 4, 7],  k=6
+# Output: True
+# Explanation: Because [23, 2, 6, 4, 7] is an continuous subarray of size 5 and sums up to 42.
+# Note:
+# The length of the array won't exceed 10,000.
+# You may assume the sum of all the numbers is in the range of a signed 32-bit integer.
+
+class Solution(object):
+    def checkSubarraySum(self, nums, k):
+        """
+        :type nums: List[int]
+        :type k: int
+        :rtype: bool
+        """
+        count = 0
+        lookup = {0: -1}
+        for i, num in enumerate(nums):
+            count += num
+            if k:
+                count %= k
+            if count in lookup:
+                if i - lookup[count] > 1:
+                    return True
+            else:
+                lookup[count] = i
+        
+        return False