120. Triangle【M】【95】【leetcode】

Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below.

For example, given the following triangle

[
[2],
[3,4],
[6,5,7],
[4,1,8,3]
]

The minimum path sum from top to bottom is

11

(i.e., 2 + 3 + 5 + 1 =
11).

Note:

Bonus point if you are able to do this using only O(n) extra space, where n is the total number of rows in the triangle.

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对于题目给的输入，每次存从顶到当前节点的最小值

保留两行即可

class Solution(object):
def minimumTotal(self, triangle):
t = triangle
l = len(t)
if l == 1 :
return t[0][0]
res1 = [99999] * l
res2 = [99999] * l

res1[0] = t[0][0]
for i in range(1,l):
res2[0] = res1[0] + t[i][0]
#print res1,res2
for j in range(1,len(t[i])):
#print i,j,t[i][j],res1[j-1],res1[j]
res2[j] = min(res1[j],res1[j - 1]) + t[i][j]

#print res1,res2
res1 = res2[:]
return min(res2)