[每日 LeetCode] 119. Pascal's Triangle II

Description:

Given a non-negative index k where k ≤ 33, return the k th index row of the Pascal's triangle.

Note that the row index starts from 0.

In Pascal's triangle, each number is the sum of the two numbers directly above it.

Example:

Input: 3
Output: [1,3,3,1]

思路：本题是 118.Pascal's Triangle 的变形，似乎在 118 题的基础上更简单了，本题只要求输出特定的行，因此只需在 118 题的基础上输出 rowIndex 行。注意数组下标是从 0 开始的。

C++ 代码

class Solution {
public:
    vector<int> getRow(int rowIndex) {
        vector<vector<int>> ret;
        for (int i=0; i<rowIndex + 1; i++){
            vector<int> temp(i+1);
            temp[0] = temp[i] = 1;
            for (int j=1; j<i;j++){
                temp[j] = ret[i-1][j] + ret[i-1][j-1];
            }
             ret.push_back(temp);
        }
        return ret[rowIndex];
    }
};

运行时间：4ms

运行内存：8.4M