【题目描述】
【方法一:动态规划】自底向上填充dp,思路没问题,但是提交超时。
def numSquares(self, n: int) -> int:
dp=[i for i in range(n+1)]
for i in range(4,n+1):
for j in range(int(n**0.5),1,-1):
if i>=j**2:
dp[i]=min(dp[i],dp[i-j*j]+1)
return dp[n]
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【方法2:BFS】
相当于从根节点0,开始向下逐层延伸,每层可加的元素是1的平方到int(n**0.5)的平方,对于每个节点均如此。
from collections import deque
class Solution:
def numSquares(self, n):
selected=[i**2 for i in range(1,int(n**0.5)+1)]
visited = set()
queue=deque([(0,0)])
while(queue):
current,height=queue.popleft()
for i in selected:
sum_= current+i
if sum_==n:
return height+1
if sum_<n and sum_ not in visited:
visited.add(sum_)
queue.append((sum_,height+1))
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