Perfect Squares
Created: September 14, 2019 by [lek-tin]
Last updated: September 14, 2019
Given a positive integer n, find the least number of perfect square numbers (for example, 1, 4, 9, 16, ...) which sum to n.
Example 1
Input: n = 12
Output: 3
Explanation: 12 = 4 + 4 + 4.
Example 2
Input: n = 13
Output: 2
Explanation: 13 = 4 + 9.
Solution
import sys
MAX_INT = sys.maxsize
class Solution:
def numSquares(self, n: int) -> int:
if n == 0:
return 0
count = [MAX_INT for _ in range(n+1)]
for i in range(1, n+1):
for j in range(1, n+1):
if j*j > n:
break
if i == j*j:
count[i] = 1
else:
# j = 0, i - j*j = i, therefore we skip j=0
count[i] = min(count[i], count[i-j*j]+1)
return count[n]