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

Python

// 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;
    }
}

Java

// 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;
    }
};

C++

# Pascal's Triangle II
# 滚动数组，时间复杂度O(n^2)，空间复杂度O(n)
def get_row(row_index):
    array = []
    for i in range(row_index + 1):
        for j in range(i - 1, 0, -1):
            array[j] = array[j - 1] + array[j]
        array.append(1)
    return array

相关题目

• Pascal's Triangle