Triangle @ LeetCode

Package Level3; import java. util. arrayList;/*** 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. **/public class S120 {public static void main (String [] args) {} public int minimumTotal (ArrayList <Integer> triangle) {int rowLen = triangle. size (); // The dp array is used to store the optimal int for each grid [] [] sum = new int [rowLen] [rowLen]; // The bottom row of ArrayList <Integer> last = triangle. get (triangle. size ()-1); for (int I = 0; I <last. size (); I ++) {sum [rowLen-1] [I] = last. get (I);} // Bottom-up DP for (int I = rowLen-2; I> = 0; I --) {ArrayList <Integer> row = triangle. get (I); for (int j = 0; j <= I; j ++) {sum [I] [j] = Math. min (sum [I + 1] [j], sum [I + 1] [j + 1]) + row. get (j) ;}} return sum [0] [0] ;}}