原题链接: https://oj.leetcode.com/problems/minimum-path-sum/

public int minPathSum(int[][] grid) {
    if (grid == null || grid.length == 0) return 0;

    int rows = grid.length;
    int cols = grid[0].length;
    int[] res = new int[cols];
    res[0] = grid[0][0];

    for (int i = 1; i < cols; i++) {
        res[i] = res[i - 1] + grid[0][i];
    }

    for (int i = 1; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            int top = res[j];
            int left = j == 0 ? Integer.MAX_VALUE : res[j - 1];
            res[j] = Math.min(top, left) + grid[i][j];
        }
    }

    return res[cols - 1];
}