leetcode--118. 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]
]

题解

a1.

class Solution {public:    vector<vector<int>> generate(int numRows) {        vector<vector<int>> ans;        for(int i = 0; i < numRows; ++i){            ans.push_back(vector<int>(i + 1, 1));            for(int j = 1; j < i; ++j){                ans[i][j] = ans[i - 1][j] + ans[i - 1][j - 1];            }        }        return ans;    }};

a2.

class Solution(object):    def generate(self, numRows):        """        :type numRows: int        :rtype: List[List[int]]        """        ans = [[1]]        for i in range(1, numRows):            ans += [map(lambda x, y: x + y, ans[-1] + [0], [0] + ans[-1])]        return ans