119. 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].

這就是楊輝三角

class Solution {
public:
    vector<int> getRow(int rowIndex) {
        vector<int> row(rowIndex + 1, 1);
        for (int i = 1; i <= rowIndex; i++) {
            int prev = 1;
            for (int j = 1; j < i; j++) {
                int temp = row[j];
                row[j] += prev;
                prev = temp;
            }
        }
        return row;
    }
};