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]
]
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//解题思路：利用一个中间vector来保存每层的数
class Solution {
public:
vector<vector<int> > generate(int numRows) {
vector<vector<int>> ans;
for(int i = 0;i < numRows;i++)
{
vector<int> cur;
if(i == 0)
cur.push_back(1);
else
{
for(int j = 0;j <= i;j++)
{
if(j == 0 || j == i) cur.push_back(1);
else cur.push_back(ans[i - 1][j] + ans[i - 1][j - 1]);
}
}
ans.push_back(cur);
} return ans;
}
};