Create ant-on-the-boundary.py

Author: kamyu104

Python/ant-on-the-boundary.py

@@ -0,0 +1,16 @@
+# Time:  O(n)
+# Space: O(1)
+
+# prefix sum
+class Solution(object):
+    def returnToBoundaryCount(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: int
+        """
+        result = curr = 0
+        for x in nums:
+            curr += x
+            if curr == 0:
+                result += 1
+        return result