leetcode Triangle及其思考

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).

这道题本身不难，它要求只使用O(n)的空间。

对于这一点，不要误解，之前有一题pascal三角的题目就是误解了。

如果限制使用的O(n)的空间，那么很有可能是对一个O(n)的空间进行重复的使用。

这道题要小心的是，对这个O(n)空间进行重复使用的时候，往往从头开始使用时不行的，

此时可以考虑从尾部往前使用，因为第k次循环可能只使用k的空间，那么对于k+1次循环来说，就有

n-k的空间可以利用

时间： 2024-11-01 16:13:21

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