leetcode笔记：Pascal's Triangle

一. 题目描写叙述

Given numRows, generate the first numRows of Pascal’s triangle.

For example, given numRows = 5,

Return:

[
     [1],
    [1,1],
   [1,2,1],
  [1,3,3,1],
 [1,4,6,4,1]
]

二. 题目分析

关于帕斯卡三角形的定义，可參考：http://baike.baidu.com/link?url=qk_-urYQnO4v6v3P4BuMtCa0tMNUqJUk4lmbkb1aqbqikBU-ndiMlTF20fq2QUjTTFTeTohZ72KFxgBnz4sJha

将该三角形的左边对齐。就行发现，tri[i][j] = tri[i-1][j-1] + tri[i-1][j]。因此这里的代码并没有什么技巧。

三. 演示样例代码

class Solution {
public:
    vector<vector<int>> generate(int numRows) {
        vector<vector<int>> result;
        if (numRows <= 0)
            return result;
        else
        {
            vector<int> temp(1, 1);
            result.push_back(temp);
            if (numRows == 1) return result;
            temp.push_back(1);
            result.push_back(temp);
            if (numRows == 2) return result;

            for (int i = 2; i < numRows; ++i)
            {
                vector<int> temp(i + 1, 1);
                for (int j = 1; j < i; ++j)
                    temp[j] = result[i - 1][j - 1] + result[i - 1][j];
                result.push_back(temp);
            }
        }
        return result;
    }
};

leetcode笔记：Pascal's Triangle

时间： 2024-12-20 01:05:31

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