Problem 81
Path sum: two ways
In the 5 by 5 matrix below, the minimal path sum from the top left to the bottom right, by only moving to the right and down, is indicated in bold red and is equal to 2427.
| 131 | 673 | 234 | 103 | 18 |
| 201 | 96 | 342 | 965 | 150 |
| 630 | 803 | 746 | 422 | 111 |
| 537 | 699 | 497 | 121 | 956 |
| 805 | 732 | 524 | 37 | 331 |
Find the minimal path sum, in matrix.txt (right click and “Save Link/Target As…”), a 31K text file containing a 80 by 80 matrix, from the top left to the bottom right by only moving right and down.
路径和：两个方向
在如下的5乘5矩阵中，从左上方到右下方始终只向右或向下移动的最小路径和为2427，由标注红色的路径给出。
| 131 | 673 | 234 | 103 | 18 |
| 201 | 96 | 342 | 965 | 150 |
| 630 | 803 | 746 | 422 | 111 |
| 537 | 699 | 497 | 121 | 956 |
| 805 | 732 | 524 | 37 | 331 |
在这个31K的文本文件matrix.txt（右击并选择“目标另存为……”）中包含了一个80乘80的矩阵，求出从该矩阵的左上方到右下方始终只向右和向下移动的最小路径和。