119. Pascal's Triangle II
119. Pascal's Triangle II
难度：Easy
内容
题目链接：https://leetcode.com/problems/pascals-triangle-ii
Given a non-negative index k where k ≤ 33, return the kth index row of the Pascal's triangle.
Note that the row index starts from 0.
In Pascal's triangle, each number is the sum of the two numbers directly above it.
Example:
Input: 3
Output: [1,3,3,1]
Follow up:
Could you optimize your algorithm to use only O(k) extra space?
思路
思路和上一题一样，只不过这里不需要存每一行的数据。
注意：和上一题相比，这里的 rowIndex + 1 = numRows
代码
class Solution {
public:
vector<int> getRow(int rowIndex) {
vector<int> res(rowIndex+1, 0);
res[0] = 1;
for (auto i = 0; i <= rowIndex; ++i)
for (auto j = i; j > 0; --j)
res[j] += res[j-1];
return res;
}
};
来源：https://github.com/xiaqunfeng/leetcode
