LeetCode——Pascal's Triangle

Given numRows, generate the first numRows of Pascal's triangle.

For example, given numRows = 5,
Return

[
     [1],
    [1,1],
   [1,2,1],
  [1,3,3,1],
 [1,4,6,4,1]
]

https://oj.leetcode.com/problems/pascals-triangle/

杨辉三角，先把两遍的值设为1，然后算中间的就是上一层的两个数相加，算当前层的时候，上一层下标一定是从0开始一直加到最后一个。

Python代码

class PascalsTriangle:
    def generate(self, numRows):
        res = []
        for i in range(1, numRows+1):
            tem = [0 for x in range(i)]
            if i == 1:
                tem[0] = 1
                # print(tem[0])
                res.append(tem)
            else:
                pos = 0
                for j in range(1, i+1):
                    if j == 1:
                        tem[0] = 1
                    elif j == i:
                        tem[j - 1] = 1
                    else:
                        tem[j-1] = res[i-2][pos] + res[i-2][pos+1]
                        pos += 1
                res.append(tem)
        return res


p = PascalsTriangle()
p.generate(5)