leetCode 118. Pascal's Triangle 數(shù)組 (楊輝三角)

118. Pascal's Triangle

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]
]

題目大意：

輸入行數(shù)，輸出如上圖所示的數(shù)組。(楊輝三角)

思路：

用雙vector來(lái)處理當(dāng)前行和下一行。

代碼如下：

class Solution {
public:
    vector<vector<int>> generate(int numRows) {
        
        vector<vector<int>> result;
        if(numRows == 0)
            return result;
        vector<int> curVec;
        vector<int> nextVec;
        
        for(int i = 0;i < numRows; i++)
        {
            for(int j = 0;j<=i;j++)
            {
                if(j == 0)
                    nextVec.push_back(1);
                else
                {
                    if(j >= curVec.size())
                        nextVec.push_back(curVec[j-1]);
                    else
                        nextVec.push_back(curVec[j] + curVec[j-1]);
                }
            }
            result.push_back(nextVec);
            curVec.swap(nextVec);
            nextVec.clear();
        }
        return result;
    }
};

2016-08-12 09:34:50