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:
import math
class Solution:
def numSquaresRec(self, n: int) -> int:
if n <= 1:
return n
if n in self.memo:
return self.memo[n]
root = int(math.sqrt(n))
minSquares = float('inf')
for k in range(1, root + 1):
minSquares = min(minSquares, 1 + self.numSquaresRec(n - k * k))
self.memo[n] = minSquares
return minSquares
def numSquares(self, n: int) -> int:
self.memo = {}
return self.numSquaresRec(n)
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