Pascal's Triangle

原题链接

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]]

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

题目给定的例子程序看着不明显，将其写成矩阵形式更容易发现规律，递归式 d[i,j] = d[i - 1, j] + d[i-1, j-1]。i为行，j为列。