Pascal's Triangle II
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?
Solution
from back to forth...
Complexity
时间复杂度 O(n2 ),空间复杂度 O(n)
Code
public class Solution {
public List<Integer> getRow(int rowIndex) {
List<Integer> res = new ArrayList<Integer>();
res.add(1);
for (int i = 1; i <= rowIndex; ++i) {
for (int j = i - 1; j >= 1; --j) {
res.set(j,res.get(j) + res.get(j-1));
}
res.add(1);
}
return res;
}
}