perfect-squares¶

Description¶

Given an integer n, return the least number of perfect square numbers that sum to n.

A perfect square is an integer that is the square of an integer; in other words, it is the product of some integer with itself. For example, 1, 4, 9, and 16 are perfect squares while 3 and 11 are not.

Example 1:

Input: n = 12
Output: 3
Explanation: 12 = 4 + 4 + 4.

Example 2:

Input: n = 13
Output: 2
Explanation: 13 = 4 + 9.

Constraints:

1 <= n <= 10⁴

Solution(Python)¶

class Solution:
    def numSquares(self, n: int) -> int:
        squareNumber = [i**2 for i in range(0, int(n ** (1 / 2)) + 1)]

        dp = [float("inf")] * (n + 1)
        dp[0] = 0
        for num in squareNumber:
            for amt in range(1, n + 1):
                if amt >= num:
                    dp[amt] = min(dp[amt], dp[amt - num] + 1)

        return dp[-1]