动态规划_leetcode279(经典栈板)

#coding=utf-8
#点评：
#递归思想加层次遍历，很经典的解题模板思想  20181220



class Solution(object):
 def numSquares(self, n):
 """
 :type n: int
 :rtype: int
 """

 pair = (n,0)
 queue = []
 queue.append(pair)

 while queue:
 curPair = queue.pop(0)
 num = curPair[0]
 step = curPair[1]

 if num == 0:
 return step

 for i in range(1,num+1):
 if num - i *i >= 0:
 nextPair = (num-i*i,step+1)
 queue.append(nextPair)
 else:
 break

class Solution2(object):
 def numSquares(self, n):
 """
 :type n: int
 :rtype: int
 """
 pair = (n, 0)
 queue = []
 queue.append(pair)

 #matrix = [[0 for i in range(3)] for i in range(3)]
 visit = [0 for i in range(n+1)]
 visit[n] = 1

 while queue:
 curPair = queue.pop(0)
 num = curPair[0]
 step = curPair[1]

 if num == 0:
 return step


 for i in range(1, num + 1):
 nextNum = num - i*i
 if nextNum >= 0:
 if visit[nextNum] == 0:
 nextPair = (nextNum, step + 1)
 queue.append(nextPair)
 visit[nextNum] = 1
 else:
 break


class Solution3(object):
 def numSquares(self, n):
 """
 :type n: int
 :rtype: int
 """
 pair = (n, 0)
 queue = []
 queue.append(pair)

 #matrix = [[0 for i in range(3)] for i in range(3)]
 visit = [0 for i in range(n+1)]
 visit[n] = 1

 while queue:
 curPair = queue.pop(0)
 num = curPair[0]
 step = curPair[1]

 if num == 0:
 return step


 for i in range(1, num + 1):
 nextNum = num - i*i
 if nextNum >= 0:
 if visit[nextNum] == 0:

 if nextNum == 0:
 return step+1

 nextPair = (nextNum, step + 1)
 queue.append(nextPair)
 visit[nextNum] = 1
 else:
 break


s = Solution2()

print s.numSquares(13)