lintcode-easy-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.

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).

 

动态规划：

创建一个和最后一行一样大小的int数组，并赋值成和最后一行一样

从倒数第二行开始往回数，把数组里的值更新成（当前这个元素）和（下一行相邻两个数中较小的数）的和

public class Solution {
    /**
     * @param triangle: a list of lists of integers.
     * @return: An integer, minimum path sum.
     */
    public int minimumTotal(int[][] triangle) {
        // write your code here
        if(triangle == null || triangle.length == 0)
            return 0;
        
        int size = triangle.length;
        
        int[] result = new int[size];
        for(int i = 0; i < size; i++){
            result[i] = triangle[size - 1][i];
        }
        
        for(int i = size - 2; i >= 0; i--){
            for(int j = 0; j <= i; j++){
                result[j] = triangle[i][j] + Math.min(result[j], result[j + 1]);
            }
        }
        
        return result[0];
    }
}