[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]]

class Solution {public:    vector<vector<int> > generate(int numRows) {        vector<vector<int> > res;        res.resize(numRows);        for(int i = 0; i < numRows; i++)            res[i].assign(i + 1, 1);        for(int i = 1; i < numRows; i++)        {            for(int j = 1; j < i; j++)                res[i][j] = res[i-1][j-1] + res[i-1][j];        }        return res;    }};

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