Triangle

Given a `triangle` array, return _the minimum path sum from top to bottom_. For each step, you may move to an adjacent number of the row below. More formally, if you are on index `i` on the current row, you may move to either index `i` or index `i + 1` on the next row.   **Example 1:** **Input:** triangle = [[2],[3,4],[6,5,7],[4,1,8,3]] **Output:** 11 **Explanation:** The triangle looks like: 2 3 4 6 5 7 4 1 8 3 The minimum path sum from top to bottom is 2 + 3 + 5 + 1 = 11 (underlined above). ``` **Example 2:** **Input:** triangle = [[-10]] **Output:** -10 ```   **Constraints:** - `1 <= triangle.length <= 200` - `triangle[0].length == 1` - `triangle[i].length == triangle[i - 1].length + 1` - `-104 <= triangle[i][j] <= 104`   **Follow up:** Could you do this using only `O(n)` extra space, where `n` is the total number of rows in the triangle?