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class Solution(object):
    def minPathSum(self, grid):
        """
        :type grid: List[List[int]]
        :rtype: int
        """
        if len(grid) == 0 or len(grid[0]) == 0:
            return 0
        rowNum = len(grid)
        colNum = len(grid[0])
        mat = [[float('inf') for _ in range(colNum+1)] for _ in range(rowNum+1)]
        mat[rowNum-1][colNum] = 0
        for row in range(rowNum-1,-1,-1):
            for col in range(colNum-1,-1,-1):
                mat[row][col] = min(mat[row+1][col], mat[row][col+1]) + grid[row][col]
        return mat[0][0]