Create modulo (%) operator.md

Author: venopyX

Tips & Tricks/modulo (%) operator.md

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+**Useful Tip: Working with `%` for Digit Operations**:
+
+When working with digits, especially in competitive programming challenges involving numbers, the modulus operator `%` is incredibly handy for various tasks:
+
+1. **Extracting Last Digit**: Use `n % 10` to extract the last digit of a number efficiently.
+   ```python
+   n = 12345
+   last_digit = n % 10  # This will give 5
+   last_two_digits = n % 100  # This will give 45
+   ```
+
+2. **Extracting Second Last Digit**: To extract the second last digit, use `(n // 10) % 10`.
+   ```python
+   n = 12345
+   second_last_digit = (n // 10) % 10  # This will give 4
+   ```
+
+3. **Extracting Digits in Reverse Order**: Use `% 10` repeatedly in a loop to extract digits in reverse order.
+   ```python
+   n = 12345
+   while n > 0:
+       digit = n % 10
+       print(digit)  # This will print digits from right to left: 5, 4, 3, 2, 1
+       n //= 10
+   ```
+
+4. **Checking Even or Odd**: Use `n % 2` to check if a number is even or odd.
+   ```python
+   n = 10
+   is_even = n % 2 == 0  # This will be True
+   ```
+
+5. **Reversing a Number**: To reverse a number, use the modulus operator in combination with integer division.
+   ```python
+   n = 12345
+   reversed_number = 0
+   while n > 0:
+       digit = n % 10
+       reversed_number = reversed_number * 10 + digit
+       n //= 10
+   ```
+
+6. **Extracting First Digit**: Use a loop with `// 10` until the number becomes less than 10 to get the first digit.
+   ```python
+   n = 12345
+   while n >= 10:
+       n //= 10
+   first_digit = n  # This will give 1
+   ```
+
+These `%` operations offer efficient solutions for various digit-related tasks in competitive programming challenges.
+
+**Note:** In above examples use of `n // 10` is to remove last digit by using integer division.