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;

    }

};