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]
]

 

 

class Solution {
public:
    vector<vector<int>> generate(int numRows) {
        vector<vector<int>> res ;
        if(numRows<=0) return res;
        vector<int> t(1,1);
        res.push_back(t);
        for(int r = 2;r<=numRows;r++){
            vector<int> temp(r,1);
            for(int i = 1;i<r-1;i++)
                temp[i] = res[r-2][i-1]+res[r-2][i];
            res.push_back(temp);
        }
        return res;
    }
};