Given a string of digits 0 – 9. The task is to count the number of substrings which when converting into integer form an even number.
Example 1:
Input : s = "1234".
Output : 6
Explanation: "2", "4", "12", "34", "234",
"1234" are 6 substring which are even.
Example 2:
Input : s = "154".
Output : 3
Explanation: "154", "54", "4" are the
even substrings.
Your Task:
You don't need to read input or print anything. Your task is to complete the function evenNumSubstring() which takes the string as inputs and returns the count of even substring.
Expected Time Complexity: O(|S|)
Expected Auxiliary Space: O(1)
Constraints:
1 ≤ |S| ≤ 10^{5}

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