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All leaked interview problems are collected from Internet.

All leaked interview problems are collected from Internet.

Given a positive integer *n*, find the least number of perfect square numbers (for example, `1, 4, 9, 16, ...`

) which sum to *n*.

For example, given *n* = `12`

, return `3`

because `12 = 4 + 4 + 4`

; given *n* = `13`

, return `2`

because `13 = 4 + 9`

.

**Credits:**

Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.

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