118.
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]
]
class Solution { public: vector<vector<int>> generate(int numRows) { vector<vector<int>> ans; if(numRows < 1) return ans; vector<int> pre, cur; pre.push_back(1); ans.push_back(pre); for(int i = 1; i < numRows; i++) { cur.push_back(1); for(int j = 0; j < pre.size()-1; j++) { cur.push_back(pre[j]+pre[j+1]); } cur.push_back(1); ans.push_back(cur); pre = cur; cur.clear(); } return ans; } };
119.
Given an index k, return the kth row of the Pascal‘s triangle.
For example, given k = 3,
Return [1,3,3,1].
class Solution { public: vector<int> getRow(int rowIndex) { vector<int> ans(rowIndex+1, 0); ans[0] = 1; for(int i = 1; i <= rowIndex; i++) { ans[i] = 1; for(int j = i-1; j > 0; j--) { ans[j] += ans[j-1]; } } return ans; } };
只开一个数组，从后向前计算。
118. 119. Pascal's Triangle -- 杨辉三角形
原文：http://www.cnblogs.com/argenbarbie/p/5450160.html