[leetcode]Triangle @ Python
2014-06-03 19:36
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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
The minimum path sum from top to bottom is
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:
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)
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