[leetcode]Triangle @ Python
原题地址:https://oj.leetcode.com/problems/triangle/
题意:
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.
解题思路:使用动态规划(dp)。需要注意的是从后往前更新!
代码:
class Solution: # @param triangle, a list of lists of integers # @return an integer def minimumTotal(self, triangle): if len(triangle) == 0: return 0 array = [0 for i in range(len(triangle))] array[0] = triangle[0][0] for i in range(1, len(triangle)): for j in range(len(triangle[i]) - 1, -1, -1): if j == len(triangle[i]) - 1: array[j] = array[j-1] + triangle[i][j] elif j == 0: array[j] = array[j] + triangle[i][j] else: array[j] = min(array[j-1], array[j]) + triangle[i][j] return min(array)