题目:
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?
代码:
class Solution { public:vector<int> getRow(int rowIndex) {vector<int> ret(rowIndex+1,1);for ( int i=0; i<=rowIndex; ++i ){for (int j=i-1; j>0; --j){ret[j] = ret[j] + ret[j-1];}}return ret;} };
tips:
采用滚动数组技巧,可以缩减空间复杂度。
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第二次过这道题,题意一开始没有看清,改了一次AC了。
class Solution { public:vector<int> getRow(int rowIndex) {vector<int> ret(rowIndex<1?1:rowIndex+1,0);ret[0] = 1;for ( int i=1; i<=rowIndex; ++i ){for ( int j=i; j>0; --j ){ret[j] = ret[j-1] + ret[j];}}return ret;} };