LeetCode-Triangle

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.

题比较简单，dp问题，并且要求空间复杂度了。

    public int minimumTotal(List<List<Integer>> triangle) {        if (triangle == null || triangle.size() == 0) return 0;        int[] dp = new int[triangle.size()];        dp[0] = triangle.get(0).get(0);        for (int i = 1; i < triangle.size(); i++) {            List<Integer> list = triangle.get(i);            dp[i] = list.get(i)+dp[i-1];            for (int j = i-1; j > 0; j--) {                dp[j] = Math.min(dp[j], dp[j-1])+list.get(j);            }            dp[0] += list.get(0);         }        int min = dp[0];        for (int n : dp) {            min = Math.min(min, n);        }        return min;    }