leetcode 118 杨辉三角形

具体查看题目链接：

https://leetcode-cn.com/problems/pascals-triangle/

class Solution {
public:
	vector<vector<int>> generate(int numRows) {
		vector<vector<int>> result;
		vector<int> up;

		for (int i = 0; i < numRows; i++)
		{
			vector<int> vec(i+1, 0);

			vec[0] = 1;
			if(i != 0) vec[i] = 1;
			for (int j = 1; j < i; j++)
			{
				vec[j] = up[j - 1] + up[j];
			}
			//up.clear();
			up.assign(vec.begin(), vec.end());
			result.push_back(vec);
		}

		return result;
	}
};