給定一個只含非負整數的m*n網格，找到一條從左上角到右下角的可以使數字和最小的路徑。
樣例
注意
你在同一時間只能向下或者向右移動一步

public class Solution {
    /**
     * @param grid: a list of lists of integers.
     * @return: An integer, minimizes the sum of all numbers along its path
     */
   public int minPathSum(int[][] grid) {
        if(null == grid)
            return 0;
        int row = grid.length;
        int col = grid[0].length;
        if(row <= 0 || col <= 0)
            return 0;
        int[][] steps = new int[row][col];
        steps[0][0] = grid[0][0];
        for(int i = 1;i < row;i++)
        {
            steps[i][0] += steps[i - 1][0] + grid[i][0];
        }
        
        for(int i = 1;i < col;i++)
        {
            steps[0][i] += steps[0][i - 1] + grid[0][i];
        }
    
        for(int i = 1;i < row;i++)
        {
            for(int j = 1;j < col;j++)
            {
                steps[i][j] = Math.min(steps[i - 1][j], steps[i][j - 1]) + grid[i][j];
            }
        }
    
        return steps[row - 1][col - 1];
    }
}