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]
]

杨辉三角的特点

class Solution {
public:
vector<vector<int>> generate(int numRows) {
vector<vector<int>> result;
vector<int > temp;
if(numRows==0)
return result;
temp.push_back(1);
result.push_back(temp);
temp.clear();
if(numRows==1)
return result;
temp.push_back(1);
temp.push_back(1);
result.push_back(temp);
if(numRows==2)
return result;
if(numRows>2)
{
vector<int>temp1;

for(int i=3; i<=numRows; i++)
{
temp1.push_back(1);
for(int j=1; j<i-1; j++)
{
temp1.push_back(temp[j]+temp[j-1]);
}
temp1.push_back(1);
result.push_back(temp1);
temp.clear();
temp = temp1;
temp1.clear();
}
}
return result;
}
};