Merge pull request #260 from 30-seconds/add-more-snippets

Add new snippets

snippets/reverse_number.md

@@ -0,0 +1,23 @@
+---
+title: reverse_number
+tags: math,string,intermediate
+---
+
+Reverses a number.
+
+- Use `str()` to convert the number to a string, slice notation to reverse it and `string.replace()` to remove the sign.
+- Use `float()` to convert the result to a number and `copysign()` to copy the original sign.
+
+```py
+from math import copysign
+
+def reverse_number(n):
+  return copysign(float(str(n)[::-1].replace('-','')), n)
+```
+
+```py
+reverse_number(981) # 189
+reverse_number(-500) # -5
+reverse_number(73.6) # 6.37
+reverse_number(-5.23) # -32.5
+```

snippets/sum_of_powers.md

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+---
+title: sum_of_powers
+tags: math,intermediate
+---
+
+Returns the sum of the powers of all the numbers from `start` to `end` (both inclusive).
+
+- Use `range()` in combination with a list comprehension to create a list of elements in the desired range raised to the given `power`, `sum()` to add the values together.
+- Omit the second argument, `power`, to use a default power of `2`.
+- Omit the third argument, `start`, to use a default starting value of `1`.
+
+```py
+def sum_of_powers(end, power = 2, start = 1):
+  return sum([(start + i) ** power for i in range(0, end + 1 - start)])
+```
+
+```py
+sum_of_powers(10) # 385
+sum_of_powers(10, 3) # 3025
+sum_of_powers(10, 3, 5) # 2925
+```