Check If One String Is a Rotation of Another

Hard ⏱ 18 min 35% acceptance ★★★★★ 4.5

Write is_rotation(s1, s2) that returns True if s2 is a rotation of s1 (i.e. s2 can be produced by moving some prefix of s1 to its end), using only a single substring-containment check — no manual rotation loop.

Examples

Example 1

Input

s1 = 'waterbottle', s2 = 'erbottlewat'

Output

True

Explanation

Rotating 'waterbottle' by moving 'wat' to the end gives 'erbottlewat'.

Example 2

Input

s1 = 'hello', s2 = 'lohel'

Output

True

Explanation

Moving 'hel' to the end of 'hello' gives 'lohel'.

Example 3

Input

s1 = 'hello', s2 = 'olelh'

Output

False

Explanation

Not a valid rotation — letters in the wrong relative order.

Constraints

s1 and s2 must be the same length to possibly be rotations; otherwise return False immediately.

Topics

StringsSubstring Search

Companies

MicrosoftAppleUber

Hints

Hint 1

Every rotation of s1 is a substring of `s1 + s1`.

Hint 2

So `s2 in (s1 + s1)` (after checking equal lengths) answers the question in one line.

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