[LeetCode]Pascal's Triangle II

题目描述:

Given an index k, return the kth row of the Pascal's triangle.

For example, given k = 3,
Return

[1,3,3,1]

.

Note:
Could you optimize your algorithm to use only O(k) extra space?

解题思路:

class Solution {
public:
vector<int> getRow(int rowIndex) {
vector<int> result;
result.push_back(1);

++rowIndex;
long s = 1;
if (rowIndex == 1) {
return result;
}

for (int j = 1; j <= rowIndex - 2; ++j) {
result.push_back(s = ((rowIndex - j) * s) / j);
}

result.push_back(1);

return result;
}
};