Pascal's Triangle II leetcode
Given an index k, return the kth 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?
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依次在上一行的基础上计算下一行,技巧就是从后向前计算,避免前面的计算影响后面的计算
vector<int> getRow(int rowIndex) { vector<int> ret(rowIndex+1, 0); ret[0] = 1; for (int i = 1; i <= rowIndex; ++i) for (int j = i; j >= 1; --j) ret[j] += ret[j - 1]; return ret; }