Python, LintCode, 20. 骰子求和

# -*- coding: utf-8 -*-
"""
Created on Mon Apr 23 15:11:22 2018

@author: HAN Jinghui
"""

class Solution:
    # @param {int} n an integer
    # @return {tuple[]} a list of tuple(sum, probability)
    def dicesSum(self, n):
        # Write your code here
        if n <= 0:
            return None
        result = [
                [],
                [1,1,1,1,1,1],
            ]
        
        # result 点数和列表
        # n 骰子数
        # i 第i个骰子
        # x 列表第i行元素数
        # j 点数和
        
        for i in range(2,n+1):
            x = 5*i+1
            result.append([0 for _ in range(x)])
             
            for j in range(x):
                if j < 6:
                    result[i][j] = (sum(result[i-1][0:j+1]))
                else:
                    result[i][j] = (sum(result[i-1][j-5:j+1]))
        
        res = result[-1]
        all = sum(res)
        other = []
        # 第i个元素代表骰子总和为n+i
        for i,item in enumerate(res):
            pro = item/all
            other.append([n+i,pro])
        return other