Pascal's Triangle II
描述
Given an index k, return the k-th 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?
分析
滚动数组。
代码
// Pascal's Triangle II
// 滚动数组，时间复杂度O(n^2)，空间复杂度O(n)
public class Solution {
public List<Integer> getRow(int rowIndex) {
List<Integer> array = new ArrayList<>();
for (int i = 0; i <= rowIndex; i++) {
for (int j = i - 1; j > 0; j--){
array.set(j, array.get(j - 1) + array.get(j));
}
array.add(1);
}
return array;
}
}
// LeetCode, Pascal's Triangle II
// 滚动数组，时间复杂度O(n^2)，空间复杂度O(n)
class Solution {
public:
vector<int> getRow(int rowIndex) {
vector<int> array;
for (int i = 0; i <= rowIndex; i++) {
for (int j = i - 1; j > 0; j--){
array[j] = array[j - 1] + array[j];
}
array.push_back(1);
}
return array;
}
};