[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]

]

 解题思路：

顺序加入每一个vector就好，其中注意元素的个数与求和关系。

class Solution {

public:

    vector<vector<int> > generate(int numRows) {

        // IMPORTANT: Please reset any member data you declared, as

        // the same Solution instance will be reused for each test case.

        vector<vector<int>> ans;

        for(int i = 0;i < numRows;i++)

        {

            vector<int> cur;

            if(i == 0)

                cur.push_back(1);

            else

            {

                for(int j = 0;j <= i;j++)

                {

                    if(j == 0 || j == i) cur.push_back(1);

                    else cur.push_back(ans[i - 1][j] + ans[i - 1][j - 1]);

                }

            }

            ans.push_back(cur);

        }

        

        return ans;

    }

};