Leetcode OJ : Triangle 动态规划 python solution

Total Accepted: 31557 Total Submissions: 116793

 

 

Given a triangle, find the minimum path sum from top to bottom.

Each step you may move to adjacent numbers on the row below.

[

     [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.

简单的动态规划

 1 import sys

 2 

 3 class Solution:

 4     # @param triangle, a list of lists of integers

 5     # @return an integer

 6     def minimumTotal(self, triangle):

 7         length = len(triangle)

 8         l = [0]

 9         l.extend([ sys.maxint for x in range(length - 1)])

10         def getLastSum(y, x):

11             return l[x] if x in range(y+1) else sys.maxint

12         for y in range(length):

13             for x in range(y, -1, -1):

14                 l[x] = triangle[y][x] + min(getLastSum(y, x), getLastSum(y, x - 1))

15         return min(l)