Create number-of-ways-to-split-a-string.py

Author: kamyu104

Python/number-of-ways-to-split-a-string.py

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+# Time:  O(n)
+# Space: O(1)
+
+class Solution(object):
+    def numWays(self, s):
+        """
+        :type s: str
+        :rtype: int
+        """
+        MOD = 10**9+7
+
+        ones = s.count('1')
+        if ones % 3:
+            return 0
+        ones //= 3
+        if ones == 0:
+            return (len(s)-1)*(len(s)-2)//2 % MOD
+        count = left = right = 0
+        for c in s:
+            if c == '1':
+                count += 1
+            if count == ones:
+                left += 1
+            elif count == 2*ones:
+                right += 1
+        return left*right % MOD