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.
class Solution(object):
def minimumTotal(self, triangle):
"""
:type triangle: List[List[int]]
:rtype: int
"""
dp = [0] * len(triangle)
dp[0] = triangle[0][0]
for i in range(1, len(triangle)):
pre = dp[0]
for j in range(len(triangle[i])):
tmp = dp[j]
if j == 0:
dp[j] = pre
elif j == len(triangle[i]) - 1:
dp[j] = pre
else:
dp[j] = min(dp[j], pre)
dp[j] += triangle[i][j]
pre = tmp
return min(dp)
