Pascal's Triangle II

1.题目描述

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?

2.解法分析

题目说要优化空间需求,实际上就是要复用空间,于是写出的代码如下:

class Solution {
public:
    vector<int> getRow(int rowIndex) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        //areslipan
        vector<int>curRow;
        curRow.push_back(1);
        if(rowIndex == 0)return curRow;
        curRow.push_back(1);
        if(rowIndex == 1)return curRow;

        vector<int>result;
        result.assign(rowIndex+1,1);

        int cur;
        int nextCur;
        for(int i = 2;i<=rowIndex;++i)
        {
            cur = result[0];
            for(int j =1;j<i;++j)
            {
                nextCur = result[j];
                result[j]=cur+result[j];
                cur = nextCur;
            }
        }

        return result;


    }
};