LeetCode – Triangle (Java)
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.
Bottom-Up (Good Solution)
We can actually start from the bottom of the triangle.
public int minimumTotal(ArrayList<ArrayList<Integer>> triangle) { int[] total = new int[triangle.size()]; int l = triangle.size() - 1; for (int i = 0; i < triangle.get(l).size(); i++) { total[i] = triangle.get(l).get(i); } // iterate from last second row for (int i = triangle.size() - 2; i >= 0; i--) { for (int j = 0; j < triangle.get(i + 1).size() - 1; j++) { total[j] = triangle.get(i).get(j) + Math.min(total[j], total[j + 1]); } } return total[0]; } |
<pre><code> String foo = "bar"; </code></pre>
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