LeetCode——Pascal's Triangle II

pickless

于 2013-09-26 00:07:51 发布

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分类专栏： Online Judge 文章标签： leetcode

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本文介绍了一个高效的算法来获取帕斯卡三角形的第K行元素，该算法仅使用O(K)的额外空间，通过迭代计算每一项值，并在过程中优化了乘除运算。

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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?

» Solve this problem

class Solution {
public:
    vector<int> getRow(int rowIndex) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        vector<int> answer;
        answer.push_back(1);
        double n = 1, m = 1;         
        for (int i = 1; i <= rowIndex; i++) {
            n *= (rowIndex - i + 1);
            m *= i;
            answer.push_back((int) (n / m + 0.5));
        }
        return answer;
    }
};