118. Pascal's Triangle
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1. 问题描述
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]
]
Tags:Array
Similar Problems:(E) Pascal‘s Triangle II
2. 解题思路
3. 代码
class Solution { public: vector<vector<int>> generate(int numRows) { vector<vector<int>> vResult; vector<int> vCurRow; vector<int> vLastRow; if (numRows <= 0) { return vResult; } if (1 <= numRows) { vCurRow.push_back(1); vResult.push_back(vCurRow); } if (2 <= numRows) { vCurRow.push_back(1); vResult.push_back(vCurRow); } vLastRow = vCurRow; if (3 <= numRows) { for (int i=3; i<=numRows; i++) { vCurRow.clear(); for (int j=0; j<i; j++) { if (0 == j) { vCurRow.push_back(1); } else if (i-1 == j) { vCurRow.push_back(1); } else { int num = vLastRow[j-1] + vLastRow[j]; vCurRow.push_back(num); } } vResult.push_back(vCurRow); vLastRow = vCurRow; } } return vResult; } };
4. 反思
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