leetcode-Pascal's Triangle

 Difficulty: Easy

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 rowIndex) {
        if(rowIndex<=0)
            return vector<vector<int> >();
        vector<int> ores(1,1);
         vector<vector<int> > finalresult;
        finalresult.push_back(ores);
        if(rowIndex==1)
            return finalresult;
        
       
        for(int i=1;i<rowIndex;++i){
            vector<int> res;
            res.push_back(1);
            int osize=ores.size();
            for(int i=0;i<osize-1;++i)
                res.push_back(ores[i]+ores[i+1]);    
            res.push_back(1);
            ores=res;
            finalresult.push_back(ores);
        }    
        return finalresult;     
    }
    
};