动态规划-数字三角形最小路径和问题

题目

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.

思路：自底向上，更新最小值

递归暴力

class Solution43 {
    public int minimumTotal(List> triangle) {
        int n=triangle.size();
        int nums[][]=new int[n][n];
        //转换成矩阵
        for(int i=0;i 
  
动态规划-代码
import java.util.*;
public class UniquePaths {
    public static void main(String args[]){
        Scanner in=new Scanner(System.in);
        while(in.hasNext()){
            int n=in.nextInt();
            List> num=new ArrayList>();
            for(int i=0;i();
                for(int j=0;j<=i;j++){
                    temp.add(in.nextInt());
                }
                num.add(new ArrayList<>(temp));
            }
            Solution42 test1=new Solution42();
            System.out.println(test1.minimumTotal(num));
        }
    }
}
class Solution42 {
    public int minimumTotal(List> triangle) {
        int n=triangle.size();
        int nums[][]=new int[n][n];
        //转换成矩阵
        for(int i=0;i=0;i--){
            for(int j=n-2;j>=0;j--){
                nums[i][j]+=Math.min(nums[i+1][j],nums[i+1][j+1]);
            }
        }
        return nums[0][0];
    }
}