Pascal's Triangle

Description

Given a non-negative integer numRows, generate the first numRows of Pascal's triangle.

In Pascal's triangle, each number is the sum of the two numbers directly above it.

Example:

Input: 5
Output:
[
     [1],
    [1,1],
   [1,2,1],
  [1,3,3,1],
 [1,4,6,4,1]
]

Solution

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