題目
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?
答案
class Solution {
public List<Integer> getRow(int rowIndex) {
// Base case, 0 or 1
if(rowIndex == 0) return Arrays.asList(1);
if(rowIndex == 1) return Arrays.asList(1, 1);
int[] list1 = new int[rowIndex+1];
int[] list2 = new int[rowIndex+1];
int[] temp = null;
list1[0] = 1;
list1[1] = 1;
for(int i = 2; i <= rowIndex; i++) {
for(int j = 1; j < i; j++) {
list2[j] = list1[j - 1] + list1[j];
}
list2[0] = 1;
list2[i] = 1;
temp = list1;
list1 = list2;
list2 = temp;
}
List<Integer> ret = new ArrayList<>();
for (int i = 0; i < list1.length; i++)
ret.add(list1[i]);
return ret;
}
}
