# 118. Pascal's Triangle

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

Approach 1: Iteration.

# Code (Python)

Approach 1:

# Code (C++)

Approach 1:

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